Add support for multiple multisigs to the processor (#377)

* Design and document a multisig rotation flow

* Make Scanner::eventualities a HashMap so it's per-key

* Don't drop eventualities, always follow through on them

Technical improvements made along the way.

* Start creating an isolate object to manage multisigs, which doesn't require being a signer

Removes key from SubstrateBlock.

* Move Scanner/Scheduler under multisigs

* Move Batch construction into MultisigManager

* Clarify "should" in Multisig Rotation docs

* Add block_number to MultisigManager, as it controls the scanner

* Move sign_plans into MultisigManager

Removes ThresholdKeys from prepare_send.

* Make SubstrateMutable an alias for MultisigManager

* Rewrite Multisig Rotation

The prior scheme had an exploit possible where funds were sent to the old
multisig, then burnt on Serai to send from the new multisig, locking liquidity
for 6 hours. While a fee could be applied to stragglers, to make this attack
unprofitable, the newly described scheme avoids all this.

* Add mini

mini is a miniature version of Serai, emphasizing Serai's nature as a
collection of independent clocks. The intended use is to identify race
conditions and prove protocols are comprehensive regarding when certain clocks
tick.

This uses loom, a prior candidate for evaluating the processor/coordinator as
free of race conditions (#361).

* Use mini to prove a race condition in the current multisig rotation docs, and prove safety of alternatives

Technically, the prior commit had mini prove the race condition.

The docs currently say the activation block of the new multisig is the block
after the next Batch's. If the two next Batches had already entered the
mempool, prior to set_keys being called, the second next Batch would be
expected to contain the new key's data yet fail to as the key wasn't public
when the Batch was actually created.

The naive solution is to create a Batch, publish it, wait until it's included,
and only then scan the next block. This sets a bound of
`Batch publication time < block time`. Optimistically, we can publish a Batch
in 24s while our shortest block time is 2m. Accordingly, we should be fine with
the naive solution which doesn't take advantage of throughput. #333 may
significantly change latency however and require an algorithm whose throughput
exceeds the rate of blocks created.

In order to re-introduce parallelization, enabling throughput, we need to
define a safe range of blocks to scan without Serai ordering the first one.
mini demonstrates safety of scanning n blocks Serai hasn't acknowledged, so
long as the first is scanned before block n+1 is (shifting the n-block window).

The docs will be updated next, to reflect this.

* Fix Multisig Rotation

I believe this is finally good enough to be final.

1) Fixes the race condition present in the prior document, as demonstrated by
mini.

`Batch`s for block `n` and `n+1`, may have been in the mempool when a
multisig's activation block was set to `n`. This would cause a potentially
distinct `Batch` for `n+1`, despite `n+1` already having a signed `Batch`.

2) Tightens when UIs should use the new multisig to prevent eclipse attacks,
and protection against `Batch` publication delays.

3) Removes liquidity fragmentation by tightening flow/handling of latency.

4) Several clarifications and documentation of reasoning.

5) Correction of "prior multisig" to "all prior multisigs" regarding historical
verification, with explanation why.

* Clarify terminology in mini

Synchronizes it from my original thoughts on potential schema to the design
actually created.

* Remove most of processor's README for a reference to docs/processor

This does drop some misc commentary, though none too beneficial. The section on
scanning, deemed sufficiently beneficial, has been moved to a document and
expanded on.

* Update scanner TODOs in line with new docs

* Correct documentation on Bitcoin::Block::time, and Block::time

* Make the scanner in MultisigManager no longer public

* Always send ConfirmKeyPair, regardless of if in-set

* Cargo.lock changes from a prior commit

* Add a policy document on defining a Canonical Chain

I accidentally committed a version of this with a few headers earlier, and this
is a proper version.

* Competent MultisigManager::new

* Update processor's comments

* Add mini to copied files

* Re-organize Scanner per multisig rotation document

* Add RUST_LOG trace targets to e2e tests

* Have the scanner wait once it gets too far ahead

Also bug fixes.

* Add activation blocks to the scanner

* Split received outputs into existing/new in MultisigManager

* Select the proper scheduler

* Schedule multisig activation as detailed in documentation

* Have the Coordinator assert if multiple `Batch`s occur within a block

While the processor used to have ack_up_to_block, enabling skips in the block
acked, support for this was removed while reworking it for multiple multisigs.
It should happen extremely infrequently.

While it would still be beneficial to have, if multiple `Batch`s could occur
within a block (with the complexity here not being worth adding that ban as a
policy), multiple `Batch`s were blocked for DoS reasons.

* Schedule payments to the proper multisig

* Correct >= to <

* Use the new multisig's key for change on schedule

* Don't report External TXs to prior multisig once deprecated

* Forward from the old multisig to the new one at all opportunities

* Move unfulfilled payments in queue from prior to new multisig

* Create MultisigsDb, splitting it out of MainDb

Drops the call to finish_signing from the Signer. While this will cause endless
re-attempts, the Signer will still consider them completed and drop them,
making this an O(n) cost at boot even if we did nothing from here.

The MultisigManager should call finish_signing once the Scanner completes the
Eventuality.

* Don't check Scanner-emitted completions, trust they are completions

Prevents needing to use async code to mark the completion and creates a
fault-free model. The current model, on fault, would cause a lack of marked
completion in the signer.

* Fix a possible panic in the processor

A shorter-chain reorg could cause this assert to trip. It's fixed by
de-duplicating the data, as the assertion checked consistency. Without the
potential for inconsistency, it's unnecessary.

* Document why an existing TODO isn't valid

* Change when we drop payments for being to the change address

The earlier timing prevents creating Plans solely to the branch address,
causing the payments to be dropped, and the TX to become an effective
aggregation TX.

* Extensively document solutions to Eventualities being potentially created after having already scanned their resolutions

* When closing, drop External/Branch outputs which don't cause progress

* Properly decide if Change outputs should be forward or not when closing

This completes all code needed to make the old multisig have a finite lifetime.

* Commentary on forwarding schemes

* Provide a 1 block window, with liquidity fragmentation risks, due to latency

On Bitcoin, this will be 10 minutes for the relevant Batch to be confirmed. On
Monero, 2 minutes. On Ethereum, ~6 minutes.

Also updates the Multisig Rotation document with the new forwarding plan.

* Implement transaction forwarding from old multisig to new multisig

Identifies a fault where Branch outputs which shouldn't be dropped may be, if
another output fulfills their next step. Locking Branch fulfillment down to
only Branch outputs is not done in this commit, but will be in the next.

* Only let Branch outputs fulfill branches

* Update TODOs

* Move the location of handling signer events to avoid a race condition

* Avoid a deadlock by using a RwLock on a single txn instead of two txns

* Move Batch ID out of the Scanner

* Increase from one block of latency on new keys activation to two

For Monero, this offered just two minutes when our latency to publish a Batch
is around a minute already. This does increase the time our liquidity can be
fragmented by up to 20 minutes (Bitcoin), yet it's a stupid attack only
possible once a week (when we rotate). Prioritizing normal users' transactions
not being subject to forwarding is more important here.

Ideally, we'd not do +2 blocks yet plus `time`, such as +10 minutes, making
this agnostic of the underlying network's block scheduling. This is a
complexity not worth it.

* Split MultisigManager::substrate_block into multiple functions

* Further tweaks to substrate_block

* Acquire a lock on all Scanner operations after calling ack_block

Gives time to call register_eventuality and initiate signing.

* Merge sign_plans into substrate_block

Also ensure the Scanner's lock isn't prematurely released.

* Use a HashMap to pass to-be-forwarded instructions, not the DB

* Successfully determine in ClosingExisting

* Move from 2 blocks of latency when rotating to 10 minutes

Superior as noted in 6d07af92ce10cfd74c17eb3400368b0150eb36d7, now trivial to
implement thanks to prior commit.

* Add note justifying measuring time in blocks when rotating

* Implement delaying of outputs received early to the new multisig per specification

* Documentation on why Branch outputs don't have the race condition concerns Change do

Also ensures 6 hours is at least N::CONFIRMATIONS, for sanity purposes.

* Remove TODO re: sanity checking Eventualities

We sanity check the Plan the Eventuality is derived from, and the Eventuality
is handled moments later (in the same file, with a clear call path). There's no
reason to add such APIs to Eventualities for a sanity check given that.

* Add TODO(now) for TODOs which must be done in this branch

Also deprecates a pair of TODOs to TODO2, and accepts the flow of the Signer
having the Eventuality.

* Correct errors in potential/future flow descriptions

* Accept having a single Plan Vec

Per the following code consuming it, there's no benefit to bifurcating it by
key.

* Only issue sign_transaction on boot for the proper signer

* Only set keys when participating in their construction

* Misc progress

Only send SubstrateBlockAck when we have a signer, as it's only used to tell
the Tributary of what Plans are being signed in response to this block.

Only immediately sets substrate_signer if session is 0.

On boot, doesn't panic if we don't have an active key (as we wouldn't if only
joining the next multisig). Continues.

* Correctly detect and set retirement block

Modifies the retirement block from first block meeting requirements to block
CONFIRMATIONS after.

Adds an ack flow to the Scanner's Confirmed event and Block event to accomplish
this, which may deadlock at this time (will be fixed shortly).

Removes an invalid await (after a point declared unsafe to use await) from
MultisigsManager::next_event.

* Remove deadlock in multisig_completed and document alternative

The alternative is simpler, albeit less efficient. There's no reason to adopt
it now, yet perhaps if it benefits modeling?

* Handle the final step of retirement, dropping the old key and setting new to existing

* Remove TODO about emitting a Block on every step

If we emit on NewAsChange, we lose the purpose of the NewAsChange period.

The only concern is if we reach ClosingExisting, and nothing has happened, then
all coins will still be in the old multisig until something finally does. This
isn't a problem worth solving, as it's latency under exceptional dead time.

* Add TODO about potentially not emitting a Block event for the reitrement block

* Restore accidentally deleted CI file

* Pair of slight tweaks

* Add missing if statement

* Disable an assertion when testing

One of the test flows currently abuses the Scanner in a way triggering it.

.github/workflows/mini-tests.yml

@@ -0,0 +1,28 @@
+name: mini/ Tests
+
+on:
+  push:
+    branches:
+      - develop
+    paths:
+      - "mini/**"
+
+  pull_request:
+    paths:
+      - "mini/**"
+
+  workflow_dispatch:
+
+jobs:
+  test-common:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@3df4ab11eba7bda6032a0b82a6bb43b11571feac
+
+      - name: Test Dependencies
+        uses: ./.github/actions/test-dependencies
+        with:
+          github-token: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Run Tests
+        run: GITHUB_CI=true RUST_BACKTRACE=1 cargo test --all-features -p mini-serai

Cargo.lock

@@ -3068,6 +3068,19 @@ dependencies = [
  "serde_json",
 ]
 
+[[package]]
+name = "generator"
+version = "0.7.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5cc16584ff22b460a382b7feec54b23d2908d858152e5739a120b949293bd74e"
+dependencies = [
+ "cc",
+ "libc",
+ "log",
+ "rustversion",
+ "windows 0.48.0",
+]
+
 [[package]]
 name = "generic-array"
 version = "0.14.7"
@@ -4505,6 +4518,19 @@ version = "0.4.20"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b5e6163cb8c49088c2c36f57875e58ccd8c87c7427f7fbd50ea6710b2f3f2e8f"
 
+[[package]]
+name = "loom"
+version = "0.7.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "86a17963e5073acf8d3e2637402657c6b467218f36fe10d696b3e1095ae019bf"
+dependencies = [
+ "cfg-if",
+ "generator",
+ "scoped-tls",
+ "tracing",
+ "tracing-subscriber 0.3.17",
+]
+
 [[package]]
 name = "lru"
 version = "0.10.1"
@@ -4615,6 +4641,15 @@ dependencies = [
  "regex-automata 0.1.10",
 ]
 
+[[package]]
+name = "matchers"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8263075bb86c5a1b1427b5ae862e8889656f126e9f77c484496e8b47cf5c5558"
+dependencies = [
+ "regex-automata 0.1.10",
+]
+
 [[package]]
 name = "matches"
 version = "0.1.10"
@@ -4701,6 +4736,13 @@ version = "0.3.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "6877bb514081ee2a7ff5ef9de3281f14a4dd4bceac4c09388074a6b5df8a139a"
 
+[[package]]
+name = "mini-serai"
+version = "0.1.0"
+dependencies = [
+ "loom",
+]
+
 [[package]]
 name = "minimal-ed448"
 version = "0.4.0"
@@ -5147,6 +5189,16 @@ version = "0.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "61807f77802ff30975e01f4f071c8ba10c022052f98b3294119f3e615d13e5be"
 
+[[package]]
+name = "nu-ansi-term"
+version = "0.46.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "77a8165726e8236064dbb45459242600304b42a5ea24ee2948e18e023bf7ba84"
+dependencies = [
+ "overload",
+ "winapi",
+]
+
 [[package]]
 name = "num-bigint"
 version = "0.4.4"
@@ -5357,6 +5409,12 @@ version = "0.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "04744f49eae99ab78e0d5c0b603ab218f515ea8cfe5a456d7629ad883a3b6e7d"
 
+[[package]]
+name = "overload"
+version = "0.1.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b15813163c1d831bf4a13c3610c05c0d03b39feb07f7e09fa234dac9b15aaf39"
+
 [[package]]
 name = "p256"
 version = "0.13.2"
@@ -7694,7 +7752,7 @@ dependencies = [
  "thiserror",
  "tracing",
  "tracing-log",
- "tracing-subscriber",
+ "tracing-subscriber 0.2.25",
 ]
 
 [[package]]
@@ -7931,6 +7989,12 @@ dependencies = [
  "zeroize",
 ]
 
+[[package]]
+name = "scoped-tls"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e1cf6437eb19a8f4a6cc0f7dca544973b0b78843adbfeb3683d1a94a0024a294"
+
 [[package]]
 name = "scopeguard"
 version = "1.2.0"
@@ -9311,7 +9375,7 @@ dependencies = [
  "sp-std",
  "tracing",
  "tracing-core",
- "tracing-subscriber",
+ "tracing-subscriber 0.2.25",
 ]
 
 [[package]]
@@ -10198,7 +10262,7 @@ dependencies = [
  "ansi_term",
  "chrono",
  "lazy_static",
- "matchers",
+ "matchers 0.0.1",
  "parking_lot 0.11.2",
  "regex",
  "serde",
@@ -10212,6 +10276,24 @@ dependencies = [
  "tracing-serde",
 ]
 
+[[package]]
+name = "tracing-subscriber"
+version = "0.3.17"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "30a651bc37f915e81f087d86e62a18eec5f79550c7faff886f7090b4ea757c77"
+dependencies = [
+ "matchers 0.1.0",
+ "nu-ansi-term",
+ "once_cell",
+ "regex",
+ "sharded-slab",
+ "smallvec",
+ "thread_local",
+ "tracing",
+ "tracing-core",
+ "tracing-log",
+]
+
 [[package]]
 name = "tributary-chain"
 version = "0.1.0"

Cargo.toml

@@ -51,6 +51,8 @@ members = [
 
   "substrate/client",
 
+  "mini",
+
   "tests/no-std",
 
   "tests/docker",

coins/bitcoin/src/wallet/mod.rs

@@ -71,6 +71,11 @@ impl ReceivedOutput {
     self.offset
   }
 
+  /// The Bitcoin output for this output.
+  pub fn output(&self) -> &TxOut {
+    &self.output
+  }
+
   /// The outpoint for this output.
   pub fn outpoint(&self) -> &OutPoint {
     &self.outpoint

coins/bitcoin/src/wallet/send.rs

@@ -116,6 +116,12 @@ impl SignableTransaction {
     self.needed_fee
   }
 
+  /// Returns the fee this transaction will use.
+  pub fn fee(&self) -> u64 {
+    self.prevouts.iter().map(|prevout| prevout.value).sum::<u64>() -
+      self.tx.output.iter().map(|prevout| prevout.value).sum::<u64>()
+  }
+
   /// Create a new SignableTransaction.
   ///
   /// If a change address is specified, any leftover funds will be sent to it if the leftover funds

coordinator/src/substrate/mod.rs

@@ -9,7 +9,7 @@ use serai_client::{
   SeraiError, Block, Serai,
   primitives::{BlockHash, NetworkId},
   validator_sets::{
-    primitives::{Session, ValidatorSet, KeyPair},
+    primitives::{ValidatorSet, KeyPair},
     ValidatorSetsEvent,
   },
   in_instructions::InInstructionsEvent,
@@ -100,28 +100,26 @@ async fn handle_key_gen<Pro: Processors>(
   set: ValidatorSet,
   key_pair: KeyPair,
 ) -> Result<(), SeraiError> {
-  if in_set(key, serai, set).await?.expect("KeyGen occurred for a set which doesn't exist") {
+  processors
-    processors
+    .send(
-      .send(
+      set.network,
-        set.network,
+      CoordinatorMessage::Substrate(
-        CoordinatorMessage::Substrate(
+        processor_messages::substrate::CoordinatorMessage::ConfirmKeyPair {
-          processor_messages::substrate::CoordinatorMessage::ConfirmKeyPair {
+          context: SubstrateContext {
-            context: SubstrateContext {
+            serai_time: block.time().unwrap() / 1000,
-              serai_time: block.time().unwrap() / 1000,
+            network_latest_finalized_block: serai
-              network_latest_finalized_block: serai
+              .get_latest_block_for_network(block.hash(), set.network)
-                .get_latest_block_for_network(block.hash(), set.network)
+              .await?
-                .await?
+              // The processor treats this as a magic value which will cause it to find a network
-                // The processor treats this as a magic value which will cause it to find a network
+              // block which has a time greater than or equal to the Serai time
-                // block which has a time greater than or equal to the Serai time
+              .unwrap_or(BlockHash([0; 32])),
-                .unwrap_or(BlockHash([0; 32])),
-            },
-            set,
-            key_pair,
           },
-        ),
+          set,
-      )
+          key_pair,
-      .await;
+        },
-  }
+      ),
+    )
+    .await;
 
   Ok(())
 }
@@ -155,13 +153,10 @@ async fn handle_batch_and_burns<Pro: Processors>(
     if let InInstructionsEvent::Batch { network, id, block: network_block } = batch {
       network_had_event(&mut burns, &mut batches, network);
 
-      // Track what Serai acknowledges as the latest block for this network
+      // Make sure this is the only Batch event for this network in this Block
-      // If this Substrate block has multiple batches, the last batch's block will overwrite the
+      // TODO: Make sure Serai rejects multiple Batchs within the same block. It should, as of an
-      // prior batches
+      // yet to be merged branch
-      // Since batches within a block are guaranteed to be ordered, thanks to their incremental ID,
+      assert!(batch_block.insert(network, network_block).is_none());
-      // the last batch will be the latest batch, so its block will be the latest block
-      // This is just a mild optimization to prevent needing an additional RPC call to grab this
-      batch_block.insert(network, network_block);
 
       // Add the batch included by this block
       batches.get_mut(&network).unwrap().push(id);
@@ -206,11 +201,6 @@ async fn handle_batch_and_burns<Pro: Processors>(
             },
             network,
             block: block.number(),
-            key: serai
-              .get_keys(ValidatorSet { network, session: Session(0) }) // TODO2
-              .await?
-              .map(|keys| keys.1.into_inner())
-              .expect("batch/burn for network which never set keys"),
             burns: burns.remove(&network).unwrap(),
             batches: batches.remove(&network).unwrap(),
           },

deny.toml

@@ -65,6 +65,8 @@ exceptions = [
 
   { allow = ["AGPL-3.0"], name = "serai-client" },
 
+  { allow = ["AGPL-3.0"], name = "mini-serai" },
+
   { allow = ["AGPL-3.0"], name = "serai-docker-tests" },
   { allow = ["AGPL-3.0"], name = "serai-message-queue-tests" },
   { allow = ["AGPL-3.0"], name = "serai-processor-tests" },

docs/policy/Canonical Chain.md

@@ -0,0 +1,72 @@
+# Canonical Chain
+
+As Serai is a network connected to many external networks, at some point we will
+likely have to ask ourselves what the canonical chain for a network is. This
+document intends to establish soft, non-binding policy, in the hopes it'll guide
+most discussions on the matter.
+
+The canonical chain is the chain Serai follows and honors transactions on. Serai
+does not guarantee operations availability nor integrity on any chains other
+than the canonical chain. Which chain is considered canonical is dependent on
+several factors.
+
+### Finalization
+
+Serai finalizes blocks from external networks onto itself. Once a block is
+finalized, it is considered irreversible. Accordingly, the primary tenet
+regarding what chain Serai will honor is the chain Serai has finalized. We can
+only assume the integrity of our coins on that chain.
+
+### Node Software
+
+Only node software which passes a quality threshold and actively identifies as
+belonging to an external network's protocol should be run. Never should a
+transformative node (a node trying to create a new network from an existing one)
+be run in place of a node actually for the external network. Beyond active
+identification, it must have community recognition as belonging.
+
+If the majority of a community actively identifying as the network stands behind
+a hard fork, it should not be considered as a new network yet the next step of
+the existing one. If a hard fork breaks Serai's integrity, it should not be
+supported.
+
+Multiple independent nodes should be run in order to reduce the likelihood of
+vulnerabilities to any specific node's faults.
+
+### Rollbacks
+
+Over time, various networks have rolled back in response to exploits. A rollback
+should undergo the same scrutiny as a hard fork. If the rollback breaks Serai's
+integrity, yet someone identifying as from the project offers to restore
+integrity out-of-band, integrity is considered kept so long as the offer is
+followed through on.
+
+Since a rollback would break Serai's finalization policy, a technical note on
+how it could be implemented is provided.
+
+Assume a blockchain from `0 .. 100` exists, with `100a ..= 500a` being rolled
+back blocks. The new chain extends from `99` with `100b ..= 200b`. Serai would
+define the canonical chain as `0 .. 100`, `100a ..= 500a`, `100b ..= 200b`, with
+`100b` building off `500a`. Serai would have to perform data-availability for
+`100a ..= 500a` (such as via a JSON file in-tree), and would have to modify the
+processor to edit its `Eventuality`s/UTXOs at `500a` back to the state at `99`.
+Any `Burn`s handled after `99` should be handled once again, if the transactions
+from `100a ..= 500a` cannot simply be carried over.
+
+### On Fault
+
+If the canonical chain does put Serai's coins into an invalid state,
+irreversibly and without amends, then the discrepancy should be amortized to all
+users as feasible, yet affected operations should otherwise halt if under
+permanent duress.
+
+For example, if Serai lists a token which has a by-governance blacklist
+function, and is blacklisted without appeal, Serai should destroy all associated
+sriXYZ and cease operations.
+
+If a bug, either in the chain or in Serai's own code, causes a loss of 10% of
+coins (without amends), operations should halt until all outputs in system can
+have their virtual amount reduced by a total amount of the loss,
+proportionalized to each output. Alternatively, Serai could decrease all token
+balances by 10%. All liquidity/swap operations should be halted until users are
+given proper time to withdraw, if they so choose, before operations resume.

docs/processor/Multisig Rotation.md

@@ -0,0 +1,176 @@
+# Multisig Rotation
+
+Substrate is expected to determine when a new validator set instance will be
+created, and with it, a new multisig. Upon the successful creation of a new
+multisig, as determined by the new multisig setting their key pair on Substrate,
+rotation begins.
+
+### Timeline
+
+The following timeline is established:
+
+1) The new multisig is created, and has its keys set on Serai. Once the next
+   `Batch` with a new external network block is published, its block becomes the
+   "queue block". The new multisig is set to activate at the "queue block", plus
+   `CONFIRMATIONS` blocks (the "activation block").
+
+   We don't use the last `Batch`'s external network block, as that `Batch` may
+   be older than `CONFIRMATIONS` blocks. Any yet-to-be-included-and-finalized
+   `Batch` will be within `CONFIRMATIONS` blocks of what any processor has
+   scanned however, as it'll wait for inclusion and finalization before
+   continuing scanning.
+
+2) Once the "activation block" itself has been finalized on Serai, UIs should
+   start exclusively using the new multisig. If the "activation block" isn't
+   finalized within `2 * CONFIRMATIONS` blocks, UIs should stop making
+   transactions to any multisig on that network.
+
+   Waiting for Serai's finalization prevents a UI from using an unfinalized
+   "activation block" before a re-organization to a shorter chain. If a
+   transaction to Serai was carried from the unfinalized "activation block"
+   to the shorter chain, it'd no longer be after the "activation block" and
+   accordingly would be ignored.
+
+   We could not wait for Serai to finalize the block, yet instead wait for the
+   block to have `CONFIRMATIONS` confirmations. This would prevent needing to
+   wait for an indeterminate amount of time for Serai to finalize the
+   "activation block", with the knowledge it should be finalized. Doing so would
+   open UIs to eclipse attacks, where they live on an alternate chain where a
+   possible "activation block" is finalized, yet Serai finalizes a distinct
+   "activation block". If the alternate chain was longer than the finalized
+   chain, the above issue would be reopened.
+
+   The reason for UIs stopping under abnormal behavior is as follows. Given a
+   sufficiently delayed `Batch` for the "activation block", UIs will use the old
+   multisig past the point it will be deprecated. Accordingly, UIs must realize
+   when `Batch`s are so delayed and continued transactions are a risk. While
+   `2 * CONFIRMATIONS` is presumably well within the 6 hour period (defined
+   below), that period exists for low-fee transactions at time of congestion. It
+   does not exist for UIs with old state, though it can be used to compensate
+   for them (reducing the tolerance for inclusion delays). `2 * CONFIRMATIONS`
+   is before the 6 hour period is enacted, preserving the tolerance for
+   inclusion delays, yet still should only happen under highly abnormal
+   circumstances.
+
+   In order to minimize the time it takes for "activation block" to be
+   finalized, a `Batch` will always be created for it, regardless of it would
+   otherwise have a `Batch` created.
+
+3) The prior multisig continues handling `Batch`s and `Burn`s for
+   `CONFIRMATIONS` blocks, plus 10 minutes, after the "activation block".
+
+   The first `CONFIRMATIONS` blocks is due to the fact the new multisig
+   shouldn't actually be sent coins during this period, making it irrelevant.
+   If coins are prematurely sent to the new multisig, they're artificially
+   delayed until the end of the `CONFIRMATIONS` blocks plus 10 minutes period.
+   This prevents an adversary from minting Serai tokens using coins in the new
+   multisig, yet then burning them to drain the prior multisig, creating a lack
+   of liquidity for several blocks.
+
+   The reason for the 10 minutes is to provide grace to honest UIs. Since UIs
+   will wait until Serai confirms the "activation block" for keys before sending
+   to them, which will take `CONFIRMATIONS` blocks plus some latency, UIs would
+   make transactions to the prior multisig past the end of this period if it was
+   `CONFIRMATIONS` alone. Since the next period is `CONFIRMATIONS` blocks, which
+   is how long transactions take to confirm, transactions made past the end of
+   this period would only received after the next period. After the next period,
+   the prior multisig adds fees and a delay to all received funds (as it
+   forwards the funds from itself to the new multisig). The 10 minutes provides
+   grace for latency.
+
+   The 10 minutes is a delay on anyone who immediately transitions to the new
+   multisig, in a no latency environment, yet the delay is preferable to fees
+   from forwarding. It also should be less than 10 minutes thanks to various
+   latencies.
+
+4) The prior multisig continues handling `Batch`s and `Burn`s for another
+   `CONFIRMATIONS` blocks.
+
+   This is for two reasons:
+
+   1) Coins sent to the new multisig still need time to gain sufficient
+      confirmations.
+   2) All outputs belonging to the prior multisig should become available within
+      `CONFIRMATIONS` blocks.
+
+   All `Burn`s handled during this period should use the new multisig for the
+   change address. This should effect a transfer of most outputs.
+
+   With the expected transfer of most outputs, and the new multisig receiving
+   new external transactions, the new multisig takes the responsibility of
+   signing all unhandled and newly emitted `Burn`s.
+
+5) For the next 6 hours, all non-`Branch` outputs received are immediately
+   forwarded to the new multisig. Only external transactions to the new multisig
+   are included in `Batch`s.
+
+   The new multisig infers the `InInstruction`, and refund address, for
+   forwarded `External` outputs via reading what they were for the original
+   `External` output.
+
+   Alternatively, the `InInstruction`, with refund address explicitly included,
+   could be included in the forwarding transaction. This may fail if the
+   `InInstruction` omitted the refund address and is too large to fit in a
+   transaction with one explicitly included. On such failure, the refund would
+   be immediately issued instead.
+
+6) Once the 6 hour period has expired, the prior multisig stops handling outputs
+   it didn't itself create. Any remaining `Eventuality`s are completed, and any
+   available/freshly available outputs are forwarded (creating new
+   `Eventuality`s which also need to successfully resolve).
+
+   Once all the 6 hour period has expired, no `Eventuality`s remain, and all
+   outputs are forwarded, the multisig publishes a final `Batch` of the first
+   block, plus `CONFIRMATIONS`, which met these conditions, regardless of if it
+   would've otherwise had a `Batch`. Then, it reports to Substrate has closed.
+   No further actions by it, nor its validators, are expected (unless those
+   validators remain present in the new multisig).
+
+7) The new multisig confirms all transactions from all prior multisigs were made
+   as expected, including the reported `Batch`s.
+
+   Unfortunately, we cannot solely check the immediately prior multisig due to
+   the ability for two sequential malicious multisigs to steal. If multisig
+   `n - 2` only transfers a fraction of its coins to multisig `n - 1`, multisig
+   `n - 1` can 'honestly' operate on the dishonest state it was given,
+   laundering it. This would let multisig `n - 1` forward the results of its
+   as-expected operations from a dishonest starting point to the new multisig,
+   and multisig `n` would attest to multisig `n - 1`'s expected (and therefore
+   presumed honest) operations, assuming liability. This would cause an honest
+   multisig to face full liability for the invalid state, causing it to be fully
+   slashed (as needed to reacquire any lost coins).
+
+   This would appear short-circuitable if multisig `n - 1` transfers coins
+   exceeding the relevant Serai tokens' supply. Serai never expects to operate
+   in an over-solvent state, yet balance should trend upwards due to a flat fee
+   applied to each received output (preventing a griefing attack). Any balance
+   greater than the tokens' supply may have had funds skimmed off the top, yet
+   they'd still guarantee the solvency of Serai without any additional fees
+   passed to users. Unfortunately, due to the requirement to verify the `Batch`s
+   published (as else the Serai tokens' supply may be manipulated), this cannot
+   actually be achieved (at least, not without a ZK proof the published `Batch`s
+   were correct).
+
+8) The new multisig reports a successful close of the prior multisig, and
+   becomes the sole multisig with full responsibilities.
+
+### Latency and Fees
+
+Slightly before the end of step 3, the new multisig should start receiving new
+external outputs. These won't be confirmed for another `CONFIRMATIONS` blocks,
+and the new multisig won't start handling `Burn`s for another `CONFIRMATIONS`
+blocks plus 10 minutes. Accordingly, the new multisig should only become
+responsible for `Burn`s shortly after it has taken ownership of the stream of
+newly received coins.
+
+Before it takes responsibility, it also should've been transferred all internal
+outputs under the standard scheduling flow. Any delayed outputs will be
+immediately forwarded, and external stragglers are only reported to Serai once
+sufficiently confirmed in the new multisig. Accordingly, liquidity should avoid
+fragmentation during rotation. The only latency should be on the 10 minutes
+present, and on delayed outputs, which should've been immediately usable, having
+to wait another `CONFIRMATIONS` blocks to be confirmed once forwarded.
+
+Immediate forwarding does unfortunately prevent batching inputs to reduce fees.
+Given immediate forwarding only applies to latent outputs, considered
+exceptional, and the protocol's fee handling ensures solvency, this is accepted.

docs/processor/Scanning.md

@@ -0,0 +1,31 @@
+# Scanning
+
+Only blocks with finality, either actual or sufficiently probabilistic, are
+operated upon. This is referred to as a block with `CONFIRMATIONS`
+confirmations, the block itself being the first confirmation.
+
+For chains which promise finality on a known schedule, `CONFIRMATIONS` is set to
+`1` and each group of finalized blocks is treated as a single block, with the
+tail block's hash representing the entire group.
+
+For chains which offer finality, on an unknown schedule, `CONFIRMATIONS` is
+still set to `1` yet blocks aren't aggregated into a group. They're handled
+individually, yet only once finalized. This allows networks which form
+finalization erratically to not have to agree on when finalizations were formed,
+solely that the blocks contained have a finalized descendant.
+
+### Notability, causing a `Batch`
+
+`Batch`s are only created for blocks which it benefits to achieve ordering on.
+These are:
+
+- Blocks which contain transactions relevant to Serai
+- Blocks which in which a new multisig activates
+- Blocks in which a prior multisig retires
+
+### Waiting for `Batch` inclusion
+
+Once a `Batch` is created, it is expected to eventually be included on Serai.
+If the `Batch` isn't included within `CONFIRMATIONS` blocks of its creation, the
+scanner will wait until its inclusion before scanning
+`batch_block + CONFIRMATIONS`.

mini/Cargo.toml

@@ -0,0 +1,17 @@
+[package]
+name = "mini-serai"
+version = "0.1.0"
+description = "A miniature version of Serai used to test for race conditions"
+license = "AGPL-3.0-only"
+repository = "https://github.com/serai-dex/serai/tree/develop/mini"
+authors = ["Luke Parker <lukeparker5132@gmail.com>"]
+keywords = []
+edition = "2021"
+publish = false
+
+[package.metadata.docs.rs]
+all-features = true
+rustdoc-args = ["--cfg", "docsrs"]
+
+[dependencies]
+loom = "0.7"

mini/LICENSE

@@ -0,0 +1,15 @@
+AGPL-3.0-only license
+
+Copyright (c) 2023 Luke Parker
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU Affero General Public License Version 3 as
+published by the Free Software Foundation.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU Affero General Public License for more details.
+
+You should have received a copy of the GNU Affero General Public License
+along with this program. If not, see <http://www.gnu.org/licenses/>.

mini/README.md

@@ -0,0 +1,27 @@
+# Mini Serai
+
+A miniature version of the Serai stack, intended to demonstrate a lack of
+system-wide race conditions in the officially stated flows.
+
+### Why
+
+When working on multiple multisigs, a race condition was noted. Originally, the
+documentation stated that the activation block of the new multisig would be the
+block after the next `Batch`'s block. This introduced a race condition, where
+since multiple `Batch`s can be signed at the same time, multiple `Batch`s can
+exist in the mempool at the same time. This could cause `Batch`s [1, 2] to
+exist in the mempool, 1 to be published (causing 2 to be the activation block of
+the new multisig), yet then the already signed 2 to be published (despite
+no longer being accurate as it only had events for a subset of keys).
+
+This effort initially modeled and tested this single race condition, yet aims to
+grow to the entire system. Then we just have to prove the actual Serai stack's
+flow reduces to the miniature flow modeled here. While further efforts are
+needed to prove Serai's implementation of the flow is itself free of race
+conditions, this is a layer of defense over the theory.
+
+### How
+
+[loom](https://docs.rs/loom) is a library which will execute a block of code
+with every possible combination of orders in order to test results aren't
+invalidated by order of execution.

mini/src/lib.rs

@@ -0,0 +1,150 @@
+use std::sync::{Arc as StdArc, RwLock as StdRwLock};
+
+use loom::{
+  thread::{self, JoinHandle},
+  sync::{Arc, RwLock, mpsc},
+};
+
+#[cfg(test)]
+mod tests;
+
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+pub struct Batch {
+  block: u64,
+  keys: Vec<u64>,
+}
+
+#[derive(Clone, PartialEq, Eq, Hash, Debug)]
+pub enum Event {
+  IncludedBatch(Batch),
+  // Allows if let else on this without clippy believing it's redundant
+  __Ignore,
+}
+
+// The amount of blocks to scan after we publish a batch, before confirming the batch was
+// included.
+// Prevents race conditions on rotation regarding when the new keys activate.
+const BATCH_FTL: u64 = 3;
+
+#[derive(Debug)]
+pub struct Serai {
+  handle: JoinHandle<()>,
+  remaining_ticks: Arc<RwLock<usize>>,
+  // Activation block, ID
+  pub active_keys: Arc<RwLock<Vec<(u64, u64)>>>,
+  pub mempool_batches: Arc<RwLock<Vec<Batch>>>,
+  pub events: mpsc::Receiver<Event>,
+  all_events_unsafe: StdArc<StdRwLock<Vec<Event>>>,
+}
+
+impl Serai {
+  #[allow(clippy::new_without_default)]
+  pub fn new(ticks: usize, mut queued_key: bool) -> Serai {
+    let remaining_ticks = Arc::new(RwLock::new(ticks));
+
+    let active_keys = Arc::new(RwLock::new(vec![(0, 0)]));
+    let mempool_batches = Arc::new(RwLock::new(vec![]));
+    let (events_sender, events_receiver) = mpsc::channel();
+    let all_events_unsafe = StdArc::new(StdRwLock::new(vec![]));
+
+    let handle = thread::spawn({
+      let remaining_ticks = remaining_ticks.clone();
+
+      let active_keys = active_keys.clone();
+      let mempool_batches = mempool_batches.clone();
+      let all_events_unsafe = all_events_unsafe.clone();
+
+      move || {
+        while {
+          let mut remaining_ticks = remaining_ticks.write().unwrap();
+          let ticking = *remaining_ticks != 0;
+          *remaining_ticks = remaining_ticks.saturating_sub(1);
+          ticking
+        } {
+          let mut batches = mempool_batches.write().unwrap();
+          if !batches.is_empty() {
+            let batch: Batch = batches.remove(0);
+
+            // Activate keys after the FTL
+            if queued_key {
+              let mut active_keys = active_keys.write().unwrap();
+              let len = active_keys.len().try_into().unwrap();
+              // TODO: active_keys is under Serai, yet the processor is the one actually with the
+              // context on when it activates
+              // This should be re-modeled as an event
+              active_keys.push((batch.block + BATCH_FTL, len));
+            }
+            queued_key = false;
+
+            let event = Event::IncludedBatch(batch);
+            events_sender.send(event.clone()).unwrap();
+            all_events_unsafe.write().unwrap().push(event);
+          }
+        }
+      }
+    });
+
+    Serai {
+      handle,
+      remaining_ticks,
+      mempool_batches,
+      active_keys,
+      events: events_receiver,
+      all_events_unsafe,
+    }
+  }
+
+  pub fn exhausted(&self) -> bool {
+    *self.remaining_ticks.read().unwrap() == 0
+  }
+
+  pub fn join(self) -> Vec<Event> {
+    self.handle.join().unwrap();
+
+    self.all_events_unsafe.read().unwrap().clone()
+  }
+}
+
+#[derive(Debug)]
+pub struct Processor {
+  handle: JoinHandle<Serai>,
+}
+
+impl Processor {
+  pub fn new(serai: Serai, blocks: u64) -> Processor {
+    let handle = thread::spawn(move || {
+      let mut last_finalized_block = 0;
+      for b in 0 .. blocks {
+        // If this block is too far ahead of Serai's last block, wait for Serai to process
+        // Note this wait only has to occur if we have a Batch which has yet to be included
+        // mini just publishes a Batch for every Block at this point in time, meaning it always has
+        // to wait
+        while b >= (last_finalized_block + BATCH_FTL) {
+          if serai.exhausted() {
+            return serai;
+          }
+          let Ok(event) = serai.events.recv() else { return serai };
+          if let Event::IncludedBatch(Batch { block, .. }) = event {
+            last_finalized_block = block;
+          }
+        }
+        serai.mempool_batches.write().unwrap().push(Batch {
+          block: b,
+          keys: serai
+            .active_keys
+            .read()
+            .unwrap()
+            .iter()
+            .filter_map(|(activation_block, id)| Some(*id).filter(|_| b >= *activation_block))
+            .collect(),
+        });
+      }
+      serai
+    });
+    Processor { handle }
+  }
+
+  pub fn join(self) -> Serai {
+    self.handle.join().unwrap()
+  }
+}

mini/src/tests/activation_race/mod.rs

@@ -0,0 +1,174 @@
+use std::{
+  collections::HashSet,
+  sync::{Arc as StdArc, RwLock as StdRwLock},
+};
+
+use crate::*;
+
+#[test]
+fn activation_race() {
+  #[derive(Debug)]
+  struct EagerProcessor {
+    handle: JoinHandle<Serai>,
+  }
+
+  impl EagerProcessor {
+    fn new(serai: Serai, batches: u64) -> EagerProcessor {
+      let handle = thread::spawn(move || {
+        for b in 0 .. batches {
+          serai.mempool_batches.write().unwrap().push(Batch {
+            block: b,
+            keys: serai
+              .active_keys
+              .read()
+              .unwrap()
+              .iter()
+              .filter_map(|(activation_block, id)| Some(*id).filter(|_| b >= *activation_block))
+              .collect(),
+          });
+        }
+        serai
+      });
+      EagerProcessor { handle }
+    }
+
+    fn join(self) -> Serai {
+      self.handle.join().unwrap()
+    }
+  }
+
+  let results = StdArc::new(StdRwLock::new(HashSet::new()));
+
+  loom::model({
+    let results = results.clone();
+    move || {
+      let serai = Serai::new(4, true);
+      let processor = EagerProcessor::new(serai, 4);
+      let serai = processor.join();
+      let events = serai.join();
+
+      results.write().unwrap().insert(events);
+    }
+  });
+
+  let results: HashSet<_> = results.read().unwrap().clone();
+  assert_eq!(results.len(), 6);
+  for result in results {
+    for (b, batch) in result.into_iter().enumerate() {
+      if b < 3 {
+        assert_eq!(
+          batch,
+          Event::IncludedBatch(Batch { block: b.try_into().unwrap(), keys: vec![0] })
+        );
+      } else {
+        let Event::IncludedBatch(batch) = batch else { panic!("unexpected event") };
+        assert_eq!(batch.block, b.try_into().unwrap());
+        assert!((batch.keys == vec![0]) || (batch.keys == vec![0, 1]));
+      }
+    }
+  }
+}
+
+#[test]
+fn sequential_solves_activation_race() {
+  #[derive(Debug)]
+  struct DelayedProcessor {
+    handle: JoinHandle<Serai>,
+  }
+
+  impl DelayedProcessor {
+    fn new(serai: Serai, batches: u64) -> DelayedProcessor {
+      let handle = thread::spawn(move || {
+        for b in 0 .. batches {
+          let batch = {
+            let mut batches = serai.mempool_batches.write().unwrap();
+            let batch = Batch {
+              block: b,
+              keys: serai
+                .active_keys
+                .read()
+                .unwrap()
+                .iter()
+                .filter_map(|(activation_block, id)| Some(*id).filter(|_| b >= *activation_block))
+                .collect(),
+            };
+            batches.push(batch.clone());
+            batch
+          };
+
+          while (!serai.exhausted()) &&
+            (serai.events.recv().unwrap() != Event::IncludedBatch(batch.clone()))
+          {
+            loom::thread::yield_now();
+          }
+        }
+        serai
+      });
+      DelayedProcessor { handle }
+    }
+
+    fn join(self) -> Serai {
+      self.handle.join().unwrap()
+    }
+  }
+
+  let results = StdArc::new(StdRwLock::new(HashSet::new()));
+
+  loom::model({
+    let results = results.clone();
+    move || {
+      let serai = Serai::new(4, true);
+      let processor = DelayedProcessor::new(serai, 4);
+      let serai = processor.join();
+      let events = serai.join();
+
+      results.write().unwrap().insert(events);
+    }
+  });
+
+  let results: HashSet<_> = results.read().unwrap().clone();
+  assert_eq!(results.len(), 5);
+  for result in results {
+    for (b, batch) in result.into_iter().enumerate() {
+      assert_eq!(
+        batch,
+        Event::IncludedBatch(Batch {
+          block: b.try_into().unwrap(),
+          keys: if b < 3 { vec![0] } else { vec![0, 1] }
+        }),
+      );
+    }
+  }
+}
+
+#[test]
+fn ftl_solves_activation_race() {
+  let results = StdArc::new(StdRwLock::new(HashSet::new()));
+
+  loom::model({
+    let results = results.clone();
+    move || {
+      let serai = Serai::new(4, true);
+      // Uses Processor since this Processor has this algorithm implemented
+      let processor = Processor::new(serai, 4);
+      let serai = processor.join();
+      let events = serai.join();
+
+      results.write().unwrap().insert(events);
+    }
+  });
+
+  let results: HashSet<_> = results.read().unwrap().clone();
+  assert_eq!(results.len(), 5);
+  for result in results {
+    for (b, batch) in result.into_iter().enumerate() {
+      assert_eq!(
+        batch,
+        Event::IncludedBatch(Batch {
+          block: b.try_into().unwrap(),
+          keys: if b < 3 { vec![0] } else { vec![0, 1] }
+        }),
+      );
+    }
+  }
+}

mini/src/tests/mod.rs

@@ -0,0 +1 @@
+mod activation_race;

orchestration/coordinator/Dockerfile

@@ -15,6 +15,7 @@ ADD message-queue /serai/message-queue
 ADD processor /serai/processor
 ADD coordinator /serai/coordinator
 ADD substrate /serai/substrate
+ADD mini /serai/mini
 ADD tests /serai/tests
 ADD Cargo.toml /serai
 ADD Cargo.lock /serai

orchestration/message-queue/Dockerfile

@@ -12,6 +12,7 @@ ADD message-queue /serai/message-queue
 ADD processor /serai/processor
 ADD coordinator /serai/coordinator
 ADD substrate /serai/substrate
+ADD mini /serai/mini
 ADD tests /serai/tests
 ADD Cargo.toml /serai
 ADD Cargo.lock /serai

orchestration/processor/Dockerfile

@@ -12,6 +12,7 @@ ADD message-queue /serai/message-queue
 ADD processor /serai/processor
 ADD coordinator /serai/coordinator
 ADD substrate /serai/substrate
+ADD mini /serai/mini
 ADD tests /serai/tests
 ADD Cargo.toml /serai
 ADD Cargo.lock /serai

orchestration/runtime/Dockerfile

@@ -20,6 +20,7 @@ ADD message-queue /serai/message-queue
 ADD processor /serai/processor
 ADD coordinator /serai/coordinator
 ADD substrate /serai/substrate
+ADD mini /serai/mini
 ADD tests /serai/tests
 ADD Cargo.toml /serai
 ADD Cargo.lock /serai

orchestration/serai/Dockerfile

@@ -12,6 +12,7 @@ ADD message-queue /serai/message-queue
 ADD processor /serai/processor
 ADD coordinator /serai/coordinator
 ADD substrate /serai/substrate
+ADD mini /serai/mini
 ADD tests /serai/tests
 ADD Cargo.toml /serai
 ADD Cargo.lock /serai

processor/README.md

@@ -1,56 +1,5 @@
 # Processor
 
-The Serai processor scans a specified chain, communicating with the coordinator.
+The Serai processor scans a specified external network, communicating with the
-
+coordinator. For details on its exact messaging flow, and overall policies,
-### Key Generation
+please view `docs/processor`.
-
-The coordinator will tell the processor if it's been included in managing a
-coin. If so, the processor is to begin the key generation protocol, relying on
-the coordinator to provided authenticated communication with the remote parties.
-
-When the key generation protocol successfully completes, the processor is
-expected to inform the coordinator so it may vote on it on the Substrate chain.
-Once the key is voted in, it'll become active.
-
-### Scanning
-
-Sufficiently confirmed block become finalized in the eyes of the procesor.
-Finalized blocks are scanned and have their outputs emitted, though not acted
-on.
-
-### Reporting
-
-The processor reports finalized blocks to the coordinator. Once the group
-acknowledges the block as finalized, they begin a threshold signing protocol
-to sign the block's outputs as a `Batch`.
-
-Once the `Batch` is signed, the processor emits an `Update` with the signed
-batch. Serai includes it, definitively ordering its outputs within the context
-of Serai.
-
-### Confirmed Outputs
-
-With the outputs' ordering, validators are able to act on them.
-
-Actions are triggered by passing the outputs to the scheduler. The scheduler
-will do one of two things:
-
-1) Use the output
-2) Accumulate it for later usage
-
-### Burn Events
-
-When the Serai chain issues a `Burn` event, the processor should send coins
-accordingly. This is done by scheduling the payments out.
-
-# TODO
-
-- Items marked TODO
-- Items marked TODO2, yet those only need to be done after protonet
-- Test the implementors of Coin against the trait API
-- Test the databases
-- Test eventuality handling
-
-- Coordinator communication
-
-Kafka? RPC ping to them, which we don't count as 'sent' until we get a pong?

processor/messages/src/lib.rs

@@ -161,7 +161,6 @@ pub mod substrate {
       context: SubstrateContext,
       network: NetworkId,
       block: u64,
-      key: Vec<u8>,
       burns: Vec<OutInstructionWithBalance>,
       batches: Vec<u32>,
     },

processor/src/coordinator.rs

@@ -25,7 +25,7 @@ impl Coordinator for MessageQueue {
   }
 
   async fn recv(&mut self) -> Message {
-    // TODO: Use a proper expected next ID
+    // TODO2: Use a proper expected next ID
     let msg = self.next(0).await;
 
     let id = msg.id;

processor/src/db.rs

@@ -1,8 +1,12 @@
 use core::marker::PhantomData;
+use std::io::Read;
+
+use scale::{Encode, Decode};
+use serai_client::validator_sets::primitives::{ValidatorSet, KeyPair};
 
 pub use serai_db::*;
 
-use crate::{Plan, networks::Network};
+use crate::networks::{Block, Network};
 
 #[derive(Debug)]
 pub struct MainDb<N: Network, D: Db>(D, PhantomData<N>);
@@ -25,74 +29,35 @@ impl<N: Network, D: Db> MainDb<N, D> {
     txn.put(Self::handled_key(id), [])
   }
 
-  fn plan_key(id: &[u8]) -> Vec<u8> {
+  fn pending_activation_key() -> Vec<u8> {
-    Self::main_key(b"plan", id)
+    Self::main_key(b"pending_activation", [])
   }
-  fn signing_key(key: &[u8]) -> Vec<u8> {
+  pub fn set_pending_activation(
-    Self::main_key(b"signing", key)
+    txn: &mut D::Transaction<'_>,
+    block_before_queue_block: <N::Block as Block<N>>::Id,
+    set: ValidatorSet,
+    key_pair: KeyPair,
+  ) {
+    let mut buf = (set, key_pair).encode();
+    buf.extend(block_before_queue_block.as_ref());
+    txn.put(Self::pending_activation_key(), buf);
   }
-  pub fn save_signing(txn: &mut D::Transaction<'_>, key: &[u8], block_number: u64, plan: &Plan<N>) {
+  pub fn pending_activation<G: Get>(
-    let id = plan.id();
+    getter: &G,
-
+  ) -> Option<(<N::Block as Block<N>>::Id, ValidatorSet, KeyPair)> {
-    {
+    if let Some(bytes) = getter.get(Self::pending_activation_key()) {
-      let mut signing = txn.get(Self::signing_key(key)).unwrap_or(vec![]);
+      if !bytes.is_empty() {
-
+        let mut slice = bytes.as_slice();
-      // If we've already noted we're signing this, return
+        let (set, key_pair) = <(ValidatorSet, KeyPair)>::decode(&mut slice).unwrap();
-      assert_eq!(signing.len() % 32, 0);
+        let mut block_before_queue_block = <N::Block as Block<N>>::Id::default();
-      for i in 0 .. (signing.len() / 32) {
+        slice.read_exact(block_before_queue_block.as_mut()).unwrap();
-        if signing[(i * 32) .. ((i + 1) * 32)] == id {
+        assert!(slice.is_empty());
-          return;
+        return Some((block_before_queue_block, set, key_pair));
-        }
-      }
-
-      signing.extend(&id);
-      txn.put(Self::signing_key(key), id);
-    }
-
-    {
-      let mut buf = block_number.to_le_bytes().to_vec();
-      plan.write(&mut buf).unwrap();
-      txn.put(Self::plan_key(&id), &buf);
-    }
-  }
-
-  pub fn signing(&self, key: &[u8]) -> Vec<(u64, Plan<N>)> {
-    let signing = self.0.get(Self::signing_key(key)).unwrap_or(vec![]);
-    let mut res = vec![];
-
-    assert_eq!(signing.len() % 32, 0);
-    for i in 0 .. (signing.len() / 32) {
-      let id = &signing[(i * 32) .. ((i + 1) * 32)];
-      let buf = self.0.get(Self::plan_key(id)).unwrap();
-
-      let block_number = u64::from_le_bytes(buf[.. 8].try_into().unwrap());
-      let plan = Plan::<N>::read::<&[u8]>(&mut &buf[16 ..]).unwrap();
-      assert_eq!(id, &plan.id());
-      res.push((block_number, plan));
-    }
-
-    res
-  }
-
-  pub fn finish_signing(&mut self, txn: &mut D::Transaction<'_>, key: &[u8], id: [u8; 32]) {
-    let mut signing = self.0.get(Self::signing_key(key)).unwrap_or(vec![]);
-    assert_eq!(signing.len() % 32, 0);
-
-    let mut found = false;
-    for i in 0 .. (signing.len() / 32) {
-      let start = i * 32;
-      let end = i + 32;
-      if signing[start .. end] == id {
-        found = true;
-        signing = [&signing[.. start], &signing[end ..]].concat().to_vec();
-        break;
       }
     }
-
+    None
-    if !found {
+  }
-      log::warn!("told to finish signing {} yet wasn't actively signing it", hex::encode(id));
+  pub fn clear_pending_activation(txn: &mut D::Transaction<'_>) {
-    }
+    txn.put(Self::pending_activation_key(), []);
-
-    txn.put(Self::signing_key(key), signing);
   }
 }

processor/src/key_gen.rs

@@ -40,9 +40,8 @@ impl<N: Network, D: Db> KeyGenDb<N, D> {
   fn save_params(txn: &mut D::Transaction<'_>, set: &ValidatorSet, params: &ThresholdParams) {
     txn.put(Self::params_key(set), bincode::serialize(params).unwrap());
   }
-  fn params<G: Get>(getter: &G, set: &ValidatorSet) -> ThresholdParams {
+  fn params<G: Get>(getter: &G, set: &ValidatorSet) -> Option<ThresholdParams> {
-    // Directly unwraps the .get() as this will only be called after being set
+    getter.get(Self::params_key(set)).map(|bytes| bincode::deserialize(&bytes).unwrap())
-    bincode::deserialize(&getter.get(Self::params_key(set)).unwrap()).unwrap()
   }
 
   // Not scoped to the set since that'd have latter attempts overwrite former
@@ -92,13 +91,13 @@ impl<N: Network, D: Db> KeyGenDb<N, D> {
   fn read_keys<G: Get>(
     getter: &G,
     key: &[u8],
-  ) -> (Vec<u8>, (ThresholdKeys<Ristretto>, ThresholdKeys<N::Curve>)) {
+  ) -> Option<(Vec<u8>, (ThresholdKeys<Ristretto>, ThresholdKeys<N::Curve>))> {
-    let keys_vec = getter.get(key).unwrap();
+    let keys_vec = getter.get(key)?;
     let mut keys_ref: &[u8] = keys_vec.as_ref();
     let substrate_keys = ThresholdKeys::new(ThresholdCore::read(&mut keys_ref).unwrap());
     let mut network_keys = ThresholdKeys::new(ThresholdCore::read(&mut keys_ref).unwrap());
     N::tweak_keys(&mut network_keys);
-    (keys_vec, (substrate_keys, network_keys))
+    Some((keys_vec, (substrate_keys, network_keys)))
   }
   fn confirm_keys(
     txn: &mut D::Transaction<'_>,
@@ -106,7 +105,8 @@ impl<N: Network, D: Db> KeyGenDb<N, D> {
     key_pair: KeyPair,
   ) -> (ThresholdKeys<Ristretto>, ThresholdKeys<N::Curve>) {
     let (keys_vec, keys) =
-      Self::read_keys(txn, &Self::generated_keys_key(set, (&key_pair.0 .0, key_pair.1.as_ref())));
+      Self::read_keys(txn, &Self::generated_keys_key(set, (&key_pair.0 .0, key_pair.1.as_ref())))
+        .unwrap();
     assert_eq!(key_pair.0 .0, keys.0.group_key().to_bytes());
     assert_eq!(
       {
@@ -121,10 +121,10 @@ impl<N: Network, D: Db> KeyGenDb<N, D> {
   fn keys<G: Get>(
     getter: &G,
     key: &<N::Curve as Ciphersuite>::G,
-  ) -> (ThresholdKeys<Ristretto>, ThresholdKeys<N::Curve>) {
+  ) -> Option<(ThresholdKeys<Ristretto>, ThresholdKeys<N::Curve>)> {
-    let res = Self::read_keys(getter, &Self::keys_key(key)).1;
+    let res = Self::read_keys(getter, &Self::keys_key(key))?.1;
     assert_eq!(&res.1.group_key(), key);
-    res
+    Some(res)
   }
 }
 
@@ -147,13 +147,21 @@ impl<N: Network, D: Db> KeyGen<N, D> {
     KeyGen { db, entropy, active_commit: HashMap::new(), active_share: HashMap::new() }
   }
 
+  pub fn in_set(&self, set: &ValidatorSet) -> bool {
+    // We determine if we're in set using if we have the parameters for a set's key generation
+    KeyGenDb::<N, D>::params(&self.db, set).is_some()
+  }
+
   pub fn keys(
     &self,
     key: &<N::Curve as Ciphersuite>::G,
-  ) -> (ThresholdKeys<Ristretto>, ThresholdKeys<N::Curve>) {
+  ) -> Option<(ThresholdKeys<Ristretto>, ThresholdKeys<N::Curve>)> {
     // This is safe, despite not having a txn, since it's a static value
     // The only concern is it may not be set when expected, or it may be set unexpectedly
-    // Since this unwraps, it being unset when expected to be set will cause a panic
+    //
+    // They're only expected to be set on boot, if confirmed. If they were confirmed yet the
+    // transaction wasn't committed, their confirmation will be re-handled
+    //
     // The only other concern is if it's set when it's not safe to use
     // The keys are only written on confirmation, and the transaction writing them is atomic to
     // every associated operation
@@ -220,7 +228,7 @@ impl<N: Network, D: Db> KeyGen<N, D> {
           panic!("commitments when already handled commitments");
         }
 
-        let params = KeyGenDb::<N, D>::params(txn, &id.set);
+        let params = KeyGenDb::<N, D>::params(txn, &id.set).unwrap();
 
         // Unwrap the machines, rebuilding them if we didn't have them in our cache
         // We won't if the processor rebooted
@@ -288,7 +296,7 @@ impl<N: Network, D: Db> KeyGen<N, D> {
       CoordinatorMessage::Shares { id, shares } => {
         info!("Received shares for {:?}", id);
 
-        let params = KeyGenDb::<N, D>::params(txn, &id.set);
+        let params = KeyGenDb::<N, D>::params(txn, &id.set).unwrap();
 
         // Same commentary on inconsistency as above exists
         let machines = self.active_share.remove(&id.set).unwrap_or_else(|| {

processor/src/main.rs

@@ -1,28 +1,19 @@
-use std::{
+use std::{sync::RwLock, time::Duration, collections::HashMap};
-  time::Duration,
-  collections::{VecDeque, HashMap},
-};
 
 use zeroize::{Zeroize, Zeroizing};
 
 use transcript::{Transcript, RecommendedTranscript};
-use ciphersuite::group::GroupEncoding;
+use ciphersuite::{group::GroupEncoding, Ciphersuite};
-use frost::{curve::Ciphersuite, ThresholdKeys};
 
-use log::{info, warn, error};
+use log::{info, warn};
 use tokio::time::sleep;
 
-use scale::{Encode, Decode};
-
 use serai_client::{
-  primitives::{MAX_DATA_LEN, BlockHash, NetworkId},
+  primitives::{BlockHash, NetworkId},
-  tokens::primitives::{OutInstruction, OutInstructionWithBalance},
+  validator_sets::primitives::{ValidatorSet, KeyPair},
-  in_instructions::primitives::{
-    Shorthand, RefundableInInstruction, InInstructionWithBalance, Batch, MAX_BATCH_SIZE,
-  },
 };
 
-use messages::{SubstrateContext, CoordinatorMessage, ProcessorMessage};
+use messages::{CoordinatorMessage, ProcessorMessage};
 
 use serai_env as env;
 
@@ -32,7 +23,7 @@ mod plan;
 pub use plan::*;
 
 mod networks;
-use networks::{OutputType, Output, PostFeeBranch, Block, Network};
+use networks::{PostFeeBranch, Block, Network, get_latest_block_number, get_block};
 #[cfg(feature = "bitcoin")]
 use networks::Bitcoin;
 #[cfg(feature = "monero")]
@@ -56,76 +47,12 @@ use signer::{SignerEvent, Signer};
 mod substrate_signer;
 use substrate_signer::{SubstrateSignerEvent, SubstrateSigner};
 
-mod scanner;
+mod multisigs;
-use scanner::{ScannerEvent, Scanner, ScannerHandle};
+use multisigs::{MultisigEvent, MultisigManager};
-
-mod scheduler;
-use scheduler::Scheduler;
 
 #[cfg(test)]
 mod tests;
 
-async fn get_latest_block_number<N: Network>(network: &N) -> usize {
-  loop {
-    match network.get_latest_block_number().await {
-      Ok(number) => {
-        return number;
-      }
-      Err(e) => {
-        error!(
-          "couldn't get the latest block number in main's error-free get_block. {} {}",
-          "this should only happen if the node is offline. error: ", e
-        );
-        sleep(Duration::from_secs(10)).await;
-      }
-    }
-  }
-}
-
-async fn get_block<N: Network>(network: &N, block_number: usize) -> N::Block {
-  loop {
-    match network.get_block(block_number).await {
-      Ok(block) => {
-        return block;
-      }
-      Err(e) => {
-        error!("couldn't get block {block_number} in main's error-free get_block. error: {}", e);
-        sleep(Duration::from_secs(10)).await;
-      }
-    }
-  }
-}
-
-async fn get_fee<N: Network>(network: &N, block_number: usize) -> N::Fee {
-  // TODO2: Use an fee representative of several blocks
-  get_block(network, block_number).await.median_fee()
-}
-
-async fn prepare_send<N: Network>(
-  network: &N,
-  keys: ThresholdKeys<N::Curve>,
-  block_number: usize,
-  fee: N::Fee,
-  plan: Plan<N>,
-) -> (Option<(N::SignableTransaction, N::Eventuality)>, Vec<PostFeeBranch>) {
-  loop {
-    match network.prepare_send(keys.clone(), block_number, plan.clone(), fee).await {
-      Ok(prepared) => {
-        return prepared;
-      }
-      Err(e) => {
-        error!("couldn't prepare a send for plan {}: {e}", hex::encode(plan.id()));
-        // The processor is either trying to create an invalid TX (fatal) or the node went
-        // offline
-        // The former requires a patch, the latter is a connection issue
-        // If the latter, this is an appropriate sleep. If the former, we should panic, yet
-        // this won't flood the console ad infinitum
-        sleep(Duration::from_secs(60)).await;
-      }
-    }
-  }
-}
-
 // Items which are mutably borrowed by Tributary.
 // Any exceptions to this have to be carefully monitored in order to ensure consistency isn't
 // violated.
@@ -164,71 +91,29 @@ struct TributaryMutable<N: Network, D: Db> {
 // Items which are mutably borrowed by Substrate.
 // Any exceptions to this have to be carefully monitored in order to ensure consistency isn't
 // violated.
-struct SubstrateMutable<N: Network, D: Db> {
-  // The scanner is expected to autonomously operate, scanning blocks as they appear.
-  // When a block is sufficiently confirmed, the scanner mutates the signer to try and get a Batch
-  // signed.
-  // The scanner itself only mutates its list of finalized blocks and in-memory state though.
-  // Disk mutations to the scan-state only happen when Substrate says to.
 
-  // This can't be mutated as soon as a Batch is signed since the mutation which occurs then is
+/*
-  // paired with the mutations caused by Burn events. Substrate's ordering determines if such a
+  The MultisigManager contains the Scanner and Schedulers.
-  // pairing exists.
-  scanner: ScannerHandle<N, D>,
 
-  // Schedulers take in new outputs, from the scanner, and payments, from Burn events on Substrate.
+  The scanner is expected to autonomously operate, scanning blocks as they appear. When a block is
-  // These are paired when possible, in the name of efficiency. Accordingly, both mutations must
+  sufficiently confirmed, the scanner causes the Substrate signer to sign a batch. It itself only
-  // happen by Substrate.
+  mutates its list of finalized blocks, to protect against re-orgs, and its in-memory state though.
-  schedulers: HashMap<Vec<u8>, Scheduler<N>>,
-}
 
-async fn sign_plans<N: Network, D: Db>(
+  Disk mutations to the scan-state only happens once the relevant `Batch` is included on Substrate.
-  txn: &mut D::Transaction<'_>,
+  It can't be mutated as soon as the `Batch` is signed as we need to know the order of `Batch`s
-  network: &N,
+  relevant to `Burn`s.
-  substrate_mutable: &mut SubstrateMutable<N, D>,
-  signers: &mut HashMap<Vec<u8>, Signer<N, D>>,
-  context: SubstrateContext,
-  plans: Vec<Plan<N>>,
-) {
-  let mut plans = VecDeque::from(plans);
 
-  let mut block_hash = <N::Block as Block<N>>::Id::default();
+  Schedulers take in new outputs, confirmed in `Batch`s, and outbound payments, triggered by
-  block_hash.as_mut().copy_from_slice(&context.network_latest_finalized_block.0);
+  `Burn`s.
-  // block_number call is safe since it unwraps
-  let block_number = substrate_mutable
-    .scanner
-    .block_number(&block_hash)
-    .await
-    .expect("told to sign_plans on a context we're not synced to");
 
-  let fee = get_fee(network, block_number).await;
+  Substrate also decides when to move to a new multisig, hence why this entire object is
+  Substate-mutable.
 
-  while let Some(plan) = plans.pop_front() {
+  Since MultisigManager should always be verifiable, and the Tributary is temporal, MultisigManager
-    let id = plan.id();
+  being entirely SubstrateMutable shows proper data pipe-lining.
-    info!("preparing plan {}: {:?}", hex::encode(id), plan);
+*/
 
-    let key = plan.key.to_bytes();
+type SubstrateMutable<N, D> = MultisigManager<D, N>;
-    MainDb::<N, D>::save_signing(txn, key.as_ref(), block_number.try_into().unwrap(), &plan);
-    let (tx, branches) =
-      prepare_send(network, signers.get_mut(key.as_ref()).unwrap().keys(), block_number, fee, plan)
-        .await;
-
-    for branch in branches {
-      substrate_mutable
-        .schedulers
-        .get_mut(key.as_ref())
-        .expect("didn't have a scheduler for a key we have a plan for")
-        .created_output::<D>(txn, branch.expected, branch.actual);
-    }
-
-    if let Some((tx, eventuality)) = tx {
-      substrate_mutable.scanner.register_eventuality(block_number, id, eventuality.clone()).await;
-      signers.get_mut(key.as_ref()).unwrap().sign_transaction(txn, id, tx, eventuality).await;
-    }
-
-    // TODO: If the TX is None, should we restore its inputs to the scheduler?
-  }
-}
 
 async fn handle_coordinator_msg<D: Db, N: Network, Co: Coordinator>(
   txn: &mut D::Transaction<'_>,
@@ -239,15 +124,18 @@ async fn handle_coordinator_msg<D: Db, N: Network, Co: Coordinator>(
   msg: &Message,
 ) {
   // If this message expects a higher block number than we have, halt until synced
-  async fn wait<N: Network, D: Db>(scanner: &ScannerHandle<N, D>, block_hash: &BlockHash) {
+  async fn wait<N: Network, D: Db>(
+    txn: &D::Transaction<'_>,
+    substrate_mutable: &SubstrateMutable<N, D>,
+    block_hash: &BlockHash,
+  ) {
     let mut needed_hash = <N::Block as Block<N>>::Id::default();
     needed_hash.as_mut().copy_from_slice(&block_hash.0);
 
-    let block_number = loop {
+    loop {
       // Ensure our scanner has scanned this block, which means our daemon has this block at
       // a sufficient depth
-      // The block_number may be set even if scanning isn't complete
+      if substrate_mutable.block_number(txn, &needed_hash).await.is_none() {
-      let Some(block_number) = scanner.block_number(&needed_hash).await else {
         warn!(
           "node is desynced. we haven't scanned {} which should happen after {} confirms",
           hex::encode(&needed_hash),
@@ -256,19 +144,10 @@ async fn handle_coordinator_msg<D: Db, N: Network, Co: Coordinator>(
         sleep(Duration::from_secs(10)).await;
         continue;
       };
-      break block_number;
+      break;
-    };
-
-    // While the scanner has cemented this block, that doesn't mean it's been scanned for all
-    // keys
-    // ram_scanned will return the lowest scanned block number out of all keys
-    // This is a safe call which fulfills the unfulfilled safety requirements from the prior call
-    while scanner.ram_scanned().await < block_number {
-      sleep(Duration::from_secs(1)).await;
     }
 
-    // TODO: Sanity check we got an AckBlock (or this is the AckBlock) for the block in
+    // TODO2: Sanity check we got an AckBlock (or this is the AckBlock) for the block in question
-    // question
 
     /*
     let synced = |context: &SubstrateContext, key| -> Result<(), ()> {
@@ -288,13 +167,38 @@ async fn handle_coordinator_msg<D: Db, N: Network, Co: Coordinator>(
   }
 
   if let Some(required) = msg.msg.required_block() {
-    // wait only reads from, it doesn't mutate, the scanner
+    // wait only reads from, it doesn't mutate, substrate_mutable
-    wait(&substrate_mutable.scanner, &required).await;
+    wait(txn, substrate_mutable, &required).await;
   }
 
-  // TODO: Shouldn't we create a txn here and pass it around as needed?
+  async fn activate_key<N: Network, D: Db>(
-  // The txn would ack this message ID. If we detect this message ID as handled in the DB,
+    network: &N,
-  // we'd move on here. Only after committing the TX would we report it as acked.
+    substrate_mutable: &mut SubstrateMutable<N, D>,
+    tributary_mutable: &mut TributaryMutable<N, D>,
+    txn: &mut D::Transaction<'_>,
+    set: ValidatorSet,
+    key_pair: KeyPair,
+    activation_number: usize,
+  ) {
+    info!("activating {set:?}'s keys at {activation_number}");
+
+    let network_key = <N as Network>::Curve::read_G::<&[u8]>(&mut key_pair.1.as_ref())
+      .expect("Substrate finalized invalid point as a network's key");
+
+    if tributary_mutable.key_gen.in_set(&set) {
+      // See TributaryMutable's struct definition for why this block is safe
+      let KeyConfirmed { substrate_keys, network_keys } =
+        tributary_mutable.key_gen.confirm(txn, set, key_pair.clone()).await;
+      if set.session.0 == 0 {
+        tributary_mutable.substrate_signer = Some(SubstrateSigner::new(N::NETWORK, substrate_keys));
+      }
+      tributary_mutable
+        .signers
+        .insert(key_pair.1.into(), Signer::new(network.clone(), network_keys));
+    }
+
+    substrate_mutable.add_key(txn, activation_number, network_key).await;
+  }
 
   match msg.msg.clone() {
     CoordinatorMessage::KeyGen(msg) => {
@@ -304,38 +208,47 @@ async fn handle_coordinator_msg<D: Db, N: Network, Co: Coordinator>(
     }
 
     CoordinatorMessage::Sign(msg) => {
-      tributary_mutable.signers.get_mut(msg.key()).unwrap().handle(txn, msg).await;
+      tributary_mutable
+        .signers
+        .get_mut(msg.key())
+        .expect("coordinator told us to sign with a signer we don't have")
+        .handle(txn, msg)
+        .await;
     }
 
     CoordinatorMessage::Coordinator(msg) => {
-      if let Some(substrate_signer) = tributary_mutable.substrate_signer.as_mut() {
+      tributary_mutable
-        substrate_signer.handle(txn, msg).await;
+        .substrate_signer
-      }
+        .as_mut()
+        .expect(
+          "coordinator told us to sign a batch when we don't have a Substrate signer at this time",
+        )
+        .handle(txn, msg)
+        .await;
     }
 
     CoordinatorMessage::Substrate(msg) => {
       match msg {
         messages::substrate::CoordinatorMessage::ConfirmKeyPair { context, set, key_pair } => {
           // This is the first key pair for this network so no block has been finalized yet
-          let activation_number = if context.network_latest_finalized_block.0 == [0; 32] {
+          // TODO: Write documentation for this in docs/
+          // TODO: Use an Option instead of a magic?
+          if context.network_latest_finalized_block.0 == [0; 32] {
             assert!(tributary_mutable.signers.is_empty());
             assert!(tributary_mutable.substrate_signer.is_none());
-            assert!(substrate_mutable.schedulers.is_empty());
+            // We can't check this as existing is no longer pub
+            // assert!(substrate_mutable.existing.as_ref().is_none());
 
             // Wait until a network's block's time exceeds Serai's time
-            // TODO: This assumes the network has a monotonic clock for its blocks' times, which
-            // isn't a viable assumption
 
             // If the latest block number is 10, then the block indexed by 1 has 10 confirms
             // 10 + 1 - 10 = 1
-            while get_block(
+            let mut block_i;
-              network,
+            while {
-              (get_latest_block_number(network).await + 1).saturating_sub(N::CONFIRMATIONS),
+              block_i =
-            )
+                (get_latest_block_number(network).await + 1).saturating_sub(N::CONFIRMATIONS);
-            .await
+              get_block(network, block_i).await.time() < context.serai_time
-            .time() <
+            } {
-              context.serai_time
-            {
               info!(
                 "serai confirmed the first key pair for a set. {} {}",
                 "we're waiting for a network's finalized block's time to exceed unix time ",
@@ -345,9 +258,7 @@ async fn handle_coordinator_msg<D: Db, N: Network, Co: Coordinator>(
             }
 
             // Find the first block to do so
-            let mut earliest =
+            let mut earliest = block_i;
-              (get_latest_block_number(network).await + 1).saturating_sub(N::CONFIRMATIONS);
-            assert!(get_block(network, earliest).await.time() >= context.serai_time);
             // earliest > 0 prevents a panic if Serai creates keys before the genesis block
             // which... should be impossible
             // Yet a prevented panic is a prevented panic
@@ -358,107 +269,103 @@ async fn handle_coordinator_msg<D: Db, N: Network, Co: Coordinator>(
             }
 
             // Use this as the activation block
-            earliest
+            let activation_number = earliest;
+
+            activate_key(
+              network,
+              substrate_mutable,
+              tributary_mutable,
+              txn,
+              set,
+              key_pair,
+              activation_number,
+            )
+            .await;
           } else {
-            let mut activation_block = <N::Block as Block<N>>::Id::default();
+            let mut block_before_queue_block = <N::Block as Block<N>>::Id::default();
-            activation_block.as_mut().copy_from_slice(&context.network_latest_finalized_block.0);
+            block_before_queue_block
-            // This block_number call is safe since it unwraps
+              .as_mut()
-            substrate_mutable
+              .copy_from_slice(&context.network_latest_finalized_block.0);
-              .scanner
+            // We can't set these keys for activation until we know their queue block, which we
-              .block_number(&activation_block)
+            // won't until the next Batch is confirmed
-              .await
+            // Set this variable so when we get the next Batch event, we can handle it
-              .expect("KeyConfirmed from context we haven't synced")
+            MainDb::<N, D>::set_pending_activation(txn, block_before_queue_block, set, key_pair);
-          };
+          }
-
-          info!("activating {set:?}'s keys at {activation_number}");
-
-          // See TributaryMutable's struct definition for why this block is safe
-          let KeyConfirmed { substrate_keys, network_keys } =
-            tributary_mutable.key_gen.confirm(txn, set, key_pair).await;
-          // TODO2: Don't immediately set this, set it once it's active
-          tributary_mutable.substrate_signer =
-            Some(SubstrateSigner::new(N::NETWORK, substrate_keys));
-
-          let key = network_keys.group_key();
-
-          substrate_mutable.scanner.rotate_key(txn, activation_number, key).await;
-          substrate_mutable
-            .schedulers
-            .insert(key.to_bytes().as_ref().to_vec(), Scheduler::<N>::new::<D>(txn, key));
-
-          tributary_mutable
-            .signers
-            .insert(key.to_bytes().as_ref().to_vec(), Signer::new(network.clone(), network_keys));
         }
 
         messages::substrate::CoordinatorMessage::SubstrateBlock {
           context,
           network: network_id,
-          block,
+          block: substrate_block,
-          key: key_vec,
           burns,
           batches,
         } => {
           assert_eq!(network_id, N::NETWORK, "coordinator sent us data for another network");
 
-          let mut block_id = <N::Block as Block<N>>::Id::default();
+          if let Some((block, set, key_pair)) = MainDb::<N, D>::pending_activation(txn) {
-          block_id.as_mut().copy_from_slice(&context.network_latest_finalized_block.0);
+            // Only run if this is a Batch belonging to a distinct block
+            if context.network_latest_finalized_block.as_ref() != block.as_ref() {
+              let mut queue_block = <N::Block as Block<N>>::Id::default();
+              queue_block.as_mut().copy_from_slice(context.network_latest_finalized_block.as_ref());
 
-          let key = <N::Curve as Ciphersuite>::read_G::<&[u8]>(&mut key_vec.as_ref()).unwrap();
+              let activation_number = substrate_mutable
+                .block_number(txn, &queue_block)
+                .await
+                .expect("KeyConfirmed from context we haven't synced") +
+                N::CONFIRMATIONS;
 
-          // We now have to acknowledge every block for this key up to the acknowledged block
+              activate_key(
-          let outputs = substrate_mutable.scanner.ack_up_to_block(txn, key, block_id).await;
+                network,
-          // Since this block was acknowledged, we no longer have to sign the batch for it
+                substrate_mutable,
+                tributary_mutable,
+                txn,
+                set,
+                key_pair,
+                activation_number,
+              )
+              .await;
+
+              MainDb::<N, D>::clear_pending_activation(txn);
+            }
+          }
+
+          // Since this block was acknowledged, we no longer have to sign the batches for it
           if let Some(substrate_signer) = tributary_mutable.substrate_signer.as_mut() {
             for batch_id in batches {
               substrate_signer.batch_signed(txn, batch_id);
             }
           }
 
-          let mut payments = vec![];
+          let (acquired_lock, to_sign) =
-          for out in burns {
+            substrate_mutable.substrate_block(txn, network, context, burns).await;
-            let OutInstructionWithBalance {
-              instruction: OutInstruction { address, data },
-              balance,
-            } = out;
-            assert_eq!(balance.coin.network(), N::NETWORK);
 
-            if let Ok(address) = N::Address::try_from(address.consume()) {
+          // Send SubstrateBlockAck, with relevant plan IDs, before we trigger the signing of these
-              // TODO: Add coin to payment
+          // plans
-              payments.push(Payment {
+          if !tributary_mutable.signers.is_empty() {
-                address,
+            coordinator
-                data: data.map(|data| data.consume()),
+              .send(messages::ProcessorMessage::Coordinator(
-                amount: balance.amount.0,
+                messages::coordinator::ProcessorMessage::SubstrateBlockAck {
-              });
+                  network: N::NETWORK,
+                  block: substrate_block,
+                  plans: to_sign.iter().map(|signable| signable.1).collect(),
+                },
+              ))
+              .await;
+          }
+
+          // See commentary in TributaryMutable for why this is safe
+          let signers = &mut tributary_mutable.signers;
+          for (key, id, tx, eventuality) in to_sign {
+            if let Some(signer) = signers.get_mut(key.to_bytes().as_ref()) {
+              signer.sign_transaction(txn, id, tx, eventuality).await;
             }
           }
 
-          let plans = substrate_mutable
+          // This is not premature, even if this block had multiple `Batch`s created, as the first
-            .schedulers
+          // `Batch` alone will trigger all Plans/Eventualities/Signs
-            .get_mut(&key_vec)
+          if acquired_lock {
-            .expect("key we don't have a scheduler for acknowledged a block")
+            substrate_mutable.release_scanner_lock().await;
-            .schedule::<D>(txn, outputs, payments);
+          }
-
-          coordinator
-            .send(ProcessorMessage::Coordinator(
-              messages::coordinator::ProcessorMessage::SubstrateBlockAck {
-                network: N::NETWORK,
-                block,
-                plans: plans.iter().map(|plan| plan.id()).collect(),
-              },
-            ))
-            .await;
-
-          sign_plans(
-            txn,
-            network,
-            substrate_mutable,
-            // See commentary in TributaryMutable for why this is safe
-            &mut tributary_mutable.signers,
-            context,
-            plans,
-          )
-          .await;
         }
       }
     }
@@ -502,63 +409,58 @@ async fn boot<N: Network, D: Db>(
 
   // We don't need to re-issue GenerateKey orders because the coordinator is expected to
   // schedule/notify us of new attempts
+  // TODO: Is this above comment still true? Not at all due to the planned lack of DKG timeouts?
   let key_gen = KeyGen::<N, _>::new(raw_db.clone(), entropy(b"key-gen_entropy"));
-  // The scanner has no long-standing orders to re-issue
-  let (mut scanner, active_keys) = Scanner::new(network.clone(), raw_db.clone());
 
-  let mut schedulers = HashMap::<Vec<u8>, Scheduler<N>>::new();
+  let (multisig_manager, current_keys, actively_signing) =
+    MultisigManager::new(raw_db, network).await;
+
   let mut substrate_signer = None;
   let mut signers = HashMap::new();
 
-  let main_db = MainDb::new(raw_db.clone());
+  let main_db = MainDb::<N, _>::new(raw_db.clone());
 
-  for key in &active_keys {
+  for (i, key) in current_keys.iter().enumerate() {
-    schedulers.insert(key.to_bytes().as_ref().to_vec(), Scheduler::from_db(raw_db, *key).unwrap());
+    let Some((substrate_keys, network_keys)) = key_gen.keys(key) else { continue };
-
+    let network_key = network_keys.group_key();
-    let (substrate_keys, network_keys) = key_gen.keys(key);
 
+    // If this is the oldest key, load the SubstrateSigner for it as the active SubstrateSigner
+    // The new key only takes responsibility once the old key is fully deprecated
+    //
     // We don't have to load any state for this since the Scanner will re-fire any events
-    // necessary
+    // necessary, only no longer scanning old blocks once Substrate acks them
-    // TODO2: This uses most recent as signer, use the active one
+    if i == 0 {
-    substrate_signer = Some(SubstrateSigner::new(N::NETWORK, substrate_keys));
+      substrate_signer = Some(SubstrateSigner::new(N::NETWORK, substrate_keys));
+    }
 
+    // The Scanner re-fires events as needed for substrate_signer yet not signer
+    // This is due to the transactions which we start signing from due to a block not being
+    // guaranteed to be signed before we stop scanning the block on reboot
+    // We could simplify the Signer flow by delaying when it acks a block, yet that'd:
+    // 1) Increase the startup time
+    // 2) Cause re-emission of Batch events, which we'd need to check the safety of
+    //    (TODO: Do anyways?)
+    // 3) Violate the attempt counter (TODO: Is this already being violated?)
     let mut signer = Signer::new(network.clone(), network_keys);
 
-    // Load any TXs being actively signed
+    // Sign any TXs being actively signed
     let key = key.to_bytes();
-    for (block_number, plan) in main_db.signing(key.as_ref()) {
+    for (plan, tx, eventuality) in &actively_signing {
-      let block_number = block_number.try_into().unwrap();
+      if plan.key == network_key {
-
+        let mut txn = raw_db.txn();
-      let fee = get_fee(network, block_number).await;
+        signer.sign_transaction(&mut txn, plan.id(), tx.clone(), eventuality.clone()).await;
-
+        // This should only have re-writes of existing data
-      let id = plan.id();
+        drop(txn);
-      info!("reloading plan {}: {:?}", hex::encode(id), plan);
+      }
-
-      let (Some((tx, eventuality)), _) =
-        prepare_send(network, signer.keys(), block_number, fee, plan).await
-      else {
-        panic!("previously created transaction is no longer being created")
-      };
-
-      scanner.register_eventuality(block_number, id, eventuality.clone()).await;
-      // TODO: Reconsider if the Signer should have the eventuality, or if just the network/scanner
-      // should
-      let mut txn = raw_db.txn();
-      signer.sign_transaction(&mut txn, id, tx, eventuality).await;
-      // This should only have re-writes of existing data
-      drop(txn);
     }
 
     signers.insert(key.as_ref().to_vec(), signer);
   }
 
-  (
+  (main_db, TributaryMutable { key_gen, substrate_signer, signers }, multisig_manager)
-    main_db,
-    TributaryMutable { key_gen, substrate_signer, signers },
-    SubstrateMutable { scanner, schedulers },
-  )
 }
 
+#[allow(clippy::await_holding_lock)] // Needed for txn, unfortunately can't be down-scoped
 async fn run<N: Network, D: Db, Co: Coordinator>(mut raw_db: D, network: N, mut coordinator: Co) {
   // We currently expect a contextless bidirectional mapping between these two values
   // (which is that any value of A can be interpreted as B and vice versa)
@@ -566,16 +468,95 @@ async fn run<N: Network, D: Db, Co: Coordinator>(mut raw_db: D, network: N, mut
   // This check ensures no network which doesn't have a bidirectional mapping is defined
   assert_eq!(<N::Block as Block<N>>::Id::default().as_ref().len(), BlockHash([0u8; 32]).0.len());
 
-  let (mut main_db, mut tributary_mutable, mut substrate_mutable) =
+  let (main_db, mut tributary_mutable, mut substrate_mutable) = boot(&mut raw_db, &network).await;
-    boot(&mut raw_db, &network).await;
 
   // We can't load this from the DB as we can't guarantee atomic increments with the ack function
   let mut last_coordinator_msg = None;
 
   loop {
+    // The following select uses this txn in both branches, hence why needing a RwLock to pass it
+    // around is needed
+    let txn = RwLock::new(raw_db.txn());
+
+    let mut outer_msg = None;
+
+    tokio::select! {
+      // This blocks the entire processor until it finishes handling this message
+      // KeyGen specifically may take a notable amount of processing time
+      // While that shouldn't be an issue in practice, as after processing an attempt it'll handle
+      // the other messages in the queue, it may be beneficial to parallelize these
+      // They could likely be parallelized by type (KeyGen, Sign, Substrate) without issue
+      msg = coordinator.recv() => {
+        let mut txn = txn.write().unwrap();
+        let txn = &mut txn;
+
+        assert_eq!(msg.id, (last_coordinator_msg.unwrap_or(msg.id - 1) + 1));
+        last_coordinator_msg = Some(msg.id);
+
+        // Only handle this if we haven't already
+        if !main_db.handled_message(msg.id) {
+          MainDb::<N, D>::handle_message(txn, msg.id);
+
+          // This is isolated to better think about how its ordered, or rather, about how the other
+          // cases aren't ordered
+          //
+          // While the coordinator messages are ordered, they're not deterministically ordered
+          // Tributary-caused messages are deterministically ordered, and Substrate-caused messages
+          // are deterministically-ordered, yet they're both shoved into a singular queue
+          // The order at which they're shoved in together isn't deterministic
+          //
+          // This is safe so long as Tributary and Substrate messages don't both expect mutable
+          // references over the same data
+          handle_coordinator_msg(
+            &mut **txn,
+            &network,
+            &mut coordinator,
+            &mut tributary_mutable,
+            &mut substrate_mutable,
+            &msg,
+          ).await;
+        }
+
+        outer_msg = Some(msg);
+      },
+
+      msg = substrate_mutable.next_event(&txn) => {
+        let mut txn = txn.write().unwrap();
+        let txn = &mut txn;
+        match msg {
+          MultisigEvent::Batches(retired_key_new_key, batches) => {
+            // Start signing this batch
+            for batch in batches {
+              info!("created batch {} ({} instructions)", batch.id, batch.instructions.len());
+
+              if let Some(substrate_signer) = tributary_mutable.substrate_signer.as_mut() {
+                substrate_signer.sign(txn, batch).await;
+              }
+            }
+
+            if let Some((retired_key, new_key)) = retired_key_new_key {
+              // Safe to mutate since all signing operations are done and no more will be added
+              tributary_mutable.signers.remove(retired_key.to_bytes().as_ref());
+              tributary_mutable.substrate_signer.take();
+              if let Some((substrate_keys, _)) = tributary_mutable.key_gen.keys(&new_key) {
+                tributary_mutable.substrate_signer =
+                  Some(SubstrateSigner::new(N::NETWORK, substrate_keys));
+              }
+            }
+          },
+          MultisigEvent::Completed(key, id, tx) => {
+            if let Some(signer) = tributary_mutable.signers.get_mut(&key) {
+              signer.completed(txn, id, tx);
+            }
+          }
+        }
+      },
+    }
+
     // Check if the signers have events
-    // The signers will only have events after the following select executes, which will then
+    // The signers will only have events after the above select executes, so having no timeout on
-    // trigger the loop again, hence why having the code here with no timer is fine
+    // the above is fine
+    // TODO: Have the Signers return these events, allowing removing these channels?
     for (key, signer) in tributary_mutable.signers.iter_mut() {
       while let Some(msg) = signer.events.pop_front() {
         match msg {
@@ -591,13 +572,6 @@ async fn run<N: Network, D: Db, Co: Coordinator>(mut raw_db: D, network: N, mut
                 tx: tx.as_ref().to_vec(),
               }))
               .await;
-
-            let mut txn = raw_db.txn();
-            // This does mutate the Scanner, yet the eventuality protocol is only run to mutate
-            // the signer, which is Tributary mutable (and what's currently being mutated)
-            substrate_mutable.scanner.drop_eventuality(id).await;
-            main_db.finish_signing(&mut txn, key, id);
-            txn.commit();
           }
         }
       }
@@ -620,136 +594,9 @@ async fn run<N: Network, D: Db, Co: Coordinator>(mut raw_db: D, network: N, mut
       }
     }
 
-    tokio::select! {
+    txn.into_inner().unwrap().commit();
-      // This blocks the entire processor until it finishes handling this message
+    if let Some(msg) = outer_msg {
-      // KeyGen specifically may take a notable amount of processing time
+      coordinator.ack(msg).await;
-      // While that shouldn't be an issue in practice, as after processing an attempt it'll handle
-      // the other messages in the queue, it may be beneficial to parallelize these
-      // They could likely be parallelized by type (KeyGen, Sign, Substrate) without issue
-      msg = coordinator.recv() => {
-        assert_eq!(msg.id, (last_coordinator_msg.unwrap_or(msg.id - 1) + 1));
-        last_coordinator_msg = Some(msg.id);
-
-        // Only handle this if we haven't already
-        if !main_db.handled_message(msg.id) {
-          let mut txn = raw_db.txn();
-          MainDb::<N, D>::handle_message(&mut txn, msg.id);
-
-          // This is isolated to better think about how its ordered, or rather, about how the other
-          // cases aren't ordered
-          //
-          // While the coordinator messages are ordered, they're not deterministically ordered
-          // Tributary-caused messages are deterministically ordered, and Substrate-caused messages
-          // are deterministically-ordered, yet they're both shoved into a singular queue
-          // The order at which they're shoved in together isn't deterministic
-          //
-          // This is safe so long as Tributary and Substrate messages don't both expect mutable
-          // references over the same data
-          handle_coordinator_msg(
-            &mut txn,
-            &network,
-            &mut coordinator,
-            &mut tributary_mutable,
-            &mut substrate_mutable,
-            &msg,
-          ).await;
-
-          txn.commit();
-        }
-
-        coordinator.ack(msg).await;
-      },
-
-      msg = substrate_mutable.scanner.events.recv() => {
-        let mut txn = raw_db.txn();
-
-        match msg.unwrap() {
-          ScannerEvent::Block { block, outputs } => {
-            let mut block_hash = [0; 32];
-            block_hash.copy_from_slice(block.as_ref());
-            // TODO: Move this out from Scanner now that the Scanner no longer handles batches
-            let mut batch_id = substrate_mutable.scanner.next_batch_id(&txn);
-
-            // start with empty batch
-            let mut batches = vec![Batch {
-              network: N::NETWORK,
-              id: batch_id,
-              block: BlockHash(block_hash),
-              instructions: vec![],
-            }];
-            for output in outputs {
-              // If these aren't externally received funds, don't handle it as an instruction
-              if output.kind() != OutputType::External {
-                continue;
-              }
-
-              let mut data = output.data();
-              let max_data_len = usize::try_from(MAX_DATA_LEN).unwrap();
-              // TODO: Refund if we hit one of the following continues
-              if data.len() > max_data_len {
-                error!(
-                  "data in output {} exceeded MAX_DATA_LEN ({MAX_DATA_LEN}): {}. skipping",
-                  hex::encode(output.id()),
-                  data.len(),
-                );
-                continue;
-              }
-
-              let Ok(shorthand) = Shorthand::decode(&mut data) else { continue };
-              let Ok(instruction) = RefundableInInstruction::try_from(shorthand) else { continue };
-
-              // TODO2: Set instruction.origin if not set (and handle refunds in general)
-              let instruction = InInstructionWithBalance {
-                instruction: instruction.instruction,
-                balance: output.balance(),
-              };
-
-              let batch = batches.last_mut().unwrap();
-              batch.instructions.push(instruction);
-
-              // check if batch is over-size
-              if batch.encode().len() > MAX_BATCH_SIZE {
-                // pop the last instruction so it's back in size
-                let instruction = batch.instructions.pop().unwrap();
-
-                // bump the id for the new batch
-                batch_id += 1;
-
-                // make a new batch with this instruction included
-                batches.push(Batch {
-                  network: N::NETWORK,
-                  id: batch_id,
-                  block: BlockHash(block_hash),
-                  instructions: vec![instruction],
-                });
-              }
-            }
-
-            // Save the next batch ID
-            substrate_mutable.scanner.set_next_batch_id(&mut txn, batch_id + 1);
-
-            // Start signing this batch
-            for batch in batches {
-              info!("created batch {} ({} instructions)", batch.id, batch.instructions.len());
-
-              if let Some(substrate_signer) = tributary_mutable.substrate_signer.as_mut() {
-                substrate_signer
-                  .sign(&mut txn, batch)
-                  .await;
-              }
-            }
-          },
-
-          ScannerEvent::Completed(id, tx) => {
-            // We don't know which signer had this plan, so inform all of them
-            for (_, signer) in tributary_mutable.signers.iter_mut() {
-              signer.eventuality_completion(&mut txn, id, &tx).await;
-            }
-          },
-        }
-
-        txn.commit();
-      },
     }
   }
 }

processor/src/multisigs/db.rs

@@ -0,0 +1,189 @@
+use core::marker::PhantomData;
+
+use ciphersuite::Ciphersuite;
+
+pub use serai_db::*;
+
+use scale::{Encode, Decode};
+use serai_client::in_instructions::primitives::InInstructionWithBalance;
+
+use crate::{
+  Get, Db, Plan,
+  networks::{Transaction, Network},
+};
+
+#[derive(Debug)]
+pub struct MultisigsDb<N: Network, D: Db>(PhantomData<N>, PhantomData<D>);
+impl<N: Network, D: Db> MultisigsDb<N, D> {
+  fn multisigs_key(dst: &'static [u8], key: impl AsRef<[u8]>) -> Vec<u8> {
+    D::key(b"MULTISIGS", dst, key)
+  }
+
+  fn next_batch_key() -> Vec<u8> {
+    Self::multisigs_key(b"next_batch", [])
+  }
+  // Set the next batch ID to use
+  pub fn set_next_batch_id(txn: &mut D::Transaction<'_>, batch: u32) {
+    txn.put(Self::next_batch_key(), batch.to_le_bytes());
+  }
+  // Get the next batch ID
+  pub fn next_batch_id<G: Get>(getter: &G) -> u32 {
+    getter.get(Self::next_batch_key()).map_or(0, |v| u32::from_le_bytes(v.try_into().unwrap()))
+  }
+
+  fn plan_key(id: &[u8]) -> Vec<u8> {
+    Self::multisigs_key(b"plan", id)
+  }
+  fn resolved_key(tx: &[u8]) -> Vec<u8> {
+    Self::multisigs_key(b"resolved", tx)
+  }
+  fn signing_key(key: &[u8]) -> Vec<u8> {
+    Self::multisigs_key(b"signing", key)
+  }
+  pub fn save_active_plan(
+    txn: &mut D::Transaction<'_>,
+    key: &[u8],
+    block_number: u64,
+    plan: &Plan<N>,
+  ) {
+    let id = plan.id();
+
+    {
+      let mut signing = txn.get(Self::signing_key(key)).unwrap_or(vec![]);
+
+      // If we've already noted we're signing this, return
+      assert_eq!(signing.len() % 32, 0);
+      for i in 0 .. (signing.len() / 32) {
+        if signing[(i * 32) .. ((i + 1) * 32)] == id {
+          return;
+        }
+      }
+
+      signing.extend(&id);
+      txn.put(Self::signing_key(key), id);
+    }
+
+    {
+      let mut buf = block_number.to_le_bytes().to_vec();
+      plan.write(&mut buf).unwrap();
+      txn.put(Self::plan_key(&id), &buf);
+    }
+  }
+
+  pub fn active_plans<G: Get>(getter: &G, key: &[u8]) -> Vec<(u64, Plan<N>)> {
+    let signing = getter.get(Self::signing_key(key)).unwrap_or(vec![]);
+    let mut res = vec![];
+
+    assert_eq!(signing.len() % 32, 0);
+    for i in 0 .. (signing.len() / 32) {
+      let id = &signing[(i * 32) .. ((i + 1) * 32)];
+      let buf = getter.get(Self::plan_key(id)).unwrap();
+
+      let block_number = u64::from_le_bytes(buf[.. 8].try_into().unwrap());
+      let plan = Plan::<N>::read::<&[u8]>(&mut &buf[8 ..]).unwrap();
+      assert_eq!(id, &plan.id());
+      res.push((block_number, plan));
+    }
+
+    res
+  }
+
+  pub fn resolved_plan<G: Get>(
+    getter: &G,
+    tx: <N::Transaction as Transaction<N>>::Id,
+  ) -> Option<[u8; 32]> {
+    getter.get(tx.as_ref()).map(|id| id.try_into().unwrap())
+  }
+  pub fn plan_by_key_with_self_change<G: Get>(
+    getter: &G,
+    key: <N::Curve as Ciphersuite>::G,
+    id: [u8; 32],
+  ) -> bool {
+    let plan =
+      Plan::<N>::read::<&[u8]>(&mut &getter.get(Self::plan_key(&id)).unwrap()[8 ..]).unwrap();
+    assert_eq!(plan.id(), id);
+    (key == plan.key) && (Some(N::change_address(plan.key)) == plan.change)
+  }
+  pub fn resolve_plan(
+    txn: &mut D::Transaction<'_>,
+    key: &[u8],
+    plan: [u8; 32],
+    resolution: <N::Transaction as Transaction<N>>::Id,
+  ) {
+    let mut signing = txn.get(Self::signing_key(key)).unwrap_or(vec![]);
+    assert_eq!(signing.len() % 32, 0);
+
+    let mut found = false;
+    for i in 0 .. (signing.len() / 32) {
+      let start = i * 32;
+      let end = i + 32;
+      if signing[start .. end] == plan {
+        found = true;
+        signing = [&signing[.. start], &signing[end ..]].concat().to_vec();
+        break;
+      }
+    }
+
+    if !found {
+      log::warn!("told to finish signing {} yet wasn't actively signing it", hex::encode(plan));
+    }
+
+    txn.put(Self::signing_key(key), signing);
+
+    txn.put(Self::resolved_key(resolution.as_ref()), plan);
+  }
+
+  fn forwarded_output_key(amount: u64) -> Vec<u8> {
+    Self::multisigs_key(b"forwarded_output", amount.to_le_bytes())
+  }
+  pub fn save_forwarded_output(
+    txn: &mut D::Transaction<'_>,
+    instruction: InInstructionWithBalance,
+  ) {
+    let key = Self::forwarded_output_key(instruction.balance.amount.0);
+    let mut existing = txn.get(&key).unwrap_or(vec![]);
+    existing.extend(instruction.encode());
+    txn.put(key, existing);
+  }
+  pub fn take_forwarded_output(
+    txn: &mut D::Transaction<'_>,
+    amount: u64,
+  ) -> Option<InInstructionWithBalance> {
+    let key = Self::forwarded_output_key(amount);
+
+    let outputs = txn.get(&key)?;
+    let mut outputs_ref = outputs.as_slice();
+
+    let res = InInstructionWithBalance::decode(&mut outputs_ref).unwrap();
+    assert!(outputs_ref.len() < outputs.len());
+    if outputs_ref.is_empty() {
+      txn.del(&key);
+    } else {
+      txn.put(&key, outputs_ref);
+    }
+    Some(res)
+  }
+
+  fn delayed_output_keys() -> Vec<u8> {
+    Self::multisigs_key(b"delayed_outputs", [])
+  }
+  pub fn save_delayed_output(txn: &mut D::Transaction<'_>, instruction: InInstructionWithBalance) {
+    let key = Self::delayed_output_keys();
+    let mut existing = txn.get(&key).unwrap_or(vec![]);
+    existing.extend(instruction.encode());
+    txn.put(key, existing);
+  }
+  pub fn take_delayed_outputs(txn: &mut D::Transaction<'_>) -> Vec<InInstructionWithBalance> {
+    let key = Self::delayed_output_keys();
+
+    let Some(outputs) = txn.get(&key) else { return vec![] };
+    txn.del(key);
+
+    let mut outputs_ref = outputs.as_slice();
+    let mut res = vec![];
+    while !outputs_ref.is_empty() {
+      res.push(InInstructionWithBalance::decode(&mut outputs_ref).unwrap());
+    }
+    res
+  }
+}

processor/src/multisigs/mod.rs

@@ -0,0 +1,927 @@
+use core::time::Duration;
+use std::{sync::RwLock, collections::HashMap};
+
+use ciphersuite::{group::GroupEncoding, Ciphersuite};
+
+use scale::{Encode, Decode};
+use messages::SubstrateContext;
+
+use serai_client::{
+  primitives::{BlockHash, MAX_DATA_LEN},
+  in_instructions::primitives::{
+    InInstructionWithBalance, Batch, RefundableInInstruction, Shorthand, MAX_BATCH_SIZE,
+  },
+  tokens::primitives::{OutInstruction, OutInstructionWithBalance},
+};
+
+use log::{info, error};
+
+use tokio::time::sleep;
+
+#[cfg(not(test))]
+mod scanner;
+#[cfg(test)]
+pub mod scanner;
+
+use scanner::{ScannerEvent, ScannerHandle, Scanner};
+
+mod db;
+use db::MultisigsDb;
+
+#[cfg(not(test))]
+mod scheduler;
+#[cfg(test)]
+pub mod scheduler;
+use scheduler::Scheduler;
+
+use crate::{
+  Get, Db, Payment, PostFeeBranch, Plan,
+  networks::{OutputType, Output, Transaction, SignableTransaction, Block, Network, get_block},
+};
+
+// InInstructionWithBalance from an external output
+fn instruction_from_output<N: Network>(output: &N::Output) -> Option<InInstructionWithBalance> {
+  assert_eq!(output.kind(), OutputType::External);
+
+  let mut data = output.data();
+  let max_data_len = usize::try_from(MAX_DATA_LEN).unwrap();
+  if data.len() > max_data_len {
+    error!(
+      "data in output {} exceeded MAX_DATA_LEN ({MAX_DATA_LEN}): {}. skipping",
+      hex::encode(output.id()),
+      data.len(),
+    );
+    None?;
+  }
+
+  let Ok(shorthand) = Shorthand::decode(&mut data) else { None? };
+  let Ok(instruction) = RefundableInInstruction::try_from(shorthand) else { None? };
+
+  // TODO2: Set instruction.origin if not set (and handle refunds in general)
+  Some(InInstructionWithBalance { instruction: instruction.instruction, balance: output.balance() })
+}
+
+#[derive(Clone, Copy, PartialEq, Eq, Debug)]
+enum RotationStep {
+  // Use the existing multisig for all actions (steps 1-3)
+  UseExisting,
+  // Use the new multisig as change (step 4)
+  NewAsChange,
+  // The existing multisig is expected to solely forward transactions at this point (step 5)
+  ForwardFromExisting,
+  // The existing multisig is expected to finish its own transactions and do nothing more
+  // (step 6)
+  ClosingExisting,
+}
+
+async fn get_fee<N: Network>(network: &N, block_number: usize) -> N::Fee {
+  // TODO2: Use an fee representative of several blocks
+  get_block(network, block_number).await.median_fee()
+}
+
+async fn prepare_send<N: Network>(
+  network: &N,
+  block_number: usize,
+  fee: N::Fee,
+  plan: Plan<N>,
+) -> (Option<(N::SignableTransaction, N::Eventuality)>, Vec<PostFeeBranch>) {
+  loop {
+    match network.prepare_send(block_number, plan.clone(), fee).await {
+      Ok(prepared) => {
+        return prepared;
+      }
+      Err(e) => {
+        error!("couldn't prepare a send for plan {}: {e}", hex::encode(plan.id()));
+        // The processor is either trying to create an invalid TX (fatal) or the node went
+        // offline
+        // The former requires a patch, the latter is a connection issue
+        // If the latter, this is an appropriate sleep. If the former, we should panic, yet
+        // this won't flood the console ad infinitum
+        sleep(Duration::from_secs(60)).await;
+      }
+    }
+  }
+}
+
+pub struct MultisigViewer<N: Network> {
+  activation_block: usize,
+  key: <N::Curve as Ciphersuite>::G,
+  scheduler: Scheduler<N>,
+}
+
+#[allow(clippy::type_complexity)]
+#[derive(Clone, Debug)]
+pub enum MultisigEvent<N: Network> {
+  // Batches to publish
+  Batches(Option<(<N::Curve as Ciphersuite>::G, <N::Curve as Ciphersuite>::G)>, Vec<Batch>),
+  // Eventuality completion found on-chain
+  Completed(Vec<u8>, [u8; 32], N::Transaction),
+}
+
+pub struct MultisigManager<D: Db, N: Network> {
+  scanner: ScannerHandle<N, D>,
+  existing: Option<MultisigViewer<N>>,
+  new: Option<MultisigViewer<N>>,
+}
+
+impl<D: Db, N: Network> MultisigManager<D, N> {
+  pub async fn new(
+    raw_db: &D,
+    network: &N,
+  ) -> (
+    Self,
+    Vec<<N::Curve as Ciphersuite>::G>,
+    Vec<(Plan<N>, N::SignableTransaction, N::Eventuality)>,
+  ) {
+    // The scanner has no long-standing orders to re-issue
+    let (mut scanner, current_keys) = Scanner::new(network.clone(), raw_db.clone());
+
+    let mut schedulers = vec![];
+
+    assert!(current_keys.len() <= 2);
+    let mut actively_signing = vec![];
+    for (_, key) in &current_keys {
+      schedulers.push(Scheduler::from_db(raw_db, *key).unwrap());
+
+      // Load any TXs being actively signed
+      let key = key.to_bytes();
+      for (block_number, plan) in MultisigsDb::<N, D>::active_plans(raw_db, key.as_ref()) {
+        let block_number = block_number.try_into().unwrap();
+
+        let fee = get_fee(network, block_number).await;
+
+        let id = plan.id();
+        info!("reloading plan {}: {:?}", hex::encode(id), plan);
+
+        let key_bytes = plan.key.to_bytes();
+
+        let (Some((tx, eventuality)), _) =
+          prepare_send(network, block_number, fee, plan.clone()).await
+        else {
+          panic!("previously created transaction is no longer being created")
+        };
+
+        scanner
+          .register_eventuality(key_bytes.as_ref(), block_number, id, eventuality.clone())
+          .await;
+        actively_signing.push((plan, tx, eventuality));
+      }
+    }
+
+    (
+      MultisigManager {
+        scanner,
+        existing: current_keys.get(0).cloned().map(|(activation_block, key)| MultisigViewer {
+          activation_block,
+          key,
+          scheduler: schedulers.remove(0),
+        }),
+        new: current_keys.get(1).cloned().map(|(activation_block, key)| MultisigViewer {
+          activation_block,
+          key,
+          scheduler: schedulers.remove(0),
+        }),
+      },
+      current_keys.into_iter().map(|(_, key)| key).collect(),
+      actively_signing,
+    )
+  }
+
+  /// Returns the block number for a block hash, if it's known and all keys have scanned the block.
+  // This is guaranteed to atomically increment so long as no new keys are added to the scanner
+  // which activate at a block before the currently highest scanned block. This is prevented by
+  // the processor waiting for `Batch` inclusion before scanning too far ahead, and activation only
+  // happening after the "too far ahead" window.
+  pub async fn block_number<G: Get>(
+    &self,
+    getter: &G,
+    hash: &<N::Block as Block<N>>::Id,
+  ) -> Option<usize> {
+    let latest = ScannerHandle::<N, D>::block_number(getter, hash)?;
+
+    // While the scanner has cemented this block, that doesn't mean it's been scanned for all
+    // keys
+    // ram_scanned will return the lowest scanned block number out of all keys
+    if latest > self.scanner.ram_scanned().await {
+      return None;
+    }
+    Some(latest)
+  }
+
+  pub async fn add_key(
+    &mut self,
+    txn: &mut D::Transaction<'_>,
+    activation_block: usize,
+    external_key: <N::Curve as Ciphersuite>::G,
+  ) {
+    self.scanner.register_key(txn, activation_block, external_key).await;
+    let viewer = Some(MultisigViewer {
+      activation_block,
+      key: external_key,
+      scheduler: Scheduler::<N>::new::<D>(txn, external_key),
+    });
+
+    if self.existing.is_none() {
+      self.existing = viewer;
+      return;
+    }
+    self.new = viewer;
+  }
+
+  fn current_rotation_step(&self, block_number: usize) -> RotationStep {
+    fn ceil_div(num: usize, denom: usize) -> usize {
+      let res = num / denom;
+      if (res * denom) == num {
+        return res;
+      }
+      res + 1
+    }
+
+    let Some(new) = self.new.as_ref() else { return RotationStep::UseExisting };
+
+    // Period numbering here has no meaning other than these the time values useful here, and the
+    // order they're built in. They have no reference/shared marker with anything else
+
+    // ESTIMATED_BLOCK_TIME_IN_SECONDS is fine to use here. While inaccurate, it shouldn't be
+    // drastically off, and even if it is, it's a hiccup to latency handling only possible when
+    // rotating. The error rate wouldn't be acceptable if it was allowed to accumulate over time,
+    // yet rotation occurs on Serai's clock, disconnecting any errors here from any prior.
+
+    // N::CONFIRMATIONS + 10 minutes
+    let period_1_start = new.activation_block +
+      N::CONFIRMATIONS +
+      ceil_div(10 * 60, N::ESTIMATED_BLOCK_TIME_IN_SECONDS);
+
+    // N::CONFIRMATIONS
+    let period_2_start = period_1_start + N::CONFIRMATIONS;
+
+    // 6 hours after period 2
+    // Also ensure 6 hours is greater than the amount of CONFIRMATIONS, for sanity purposes
+    let period_3_start =
+      period_2_start + ((6 * 60 * 60) / N::ESTIMATED_BLOCK_TIME_IN_SECONDS).max(N::CONFIRMATIONS);
+
+    if block_number < period_1_start {
+      RotationStep::UseExisting
+    } else if block_number < period_2_start {
+      RotationStep::NewAsChange
+    } else if block_number < period_3_start {
+      RotationStep::ForwardFromExisting
+    } else {
+      RotationStep::ClosingExisting
+    }
+  }
+
+  // Convert new Burns to Payments.
+  //
+  // Also moves payments from the old Scheduler to the new multisig if the step calls for it.
+  fn burns_to_payments(
+    &mut self,
+    txn: &mut D::Transaction<'_>,
+    step: RotationStep,
+    burns: Vec<OutInstructionWithBalance>,
+  ) -> (Vec<Payment<N>>, Vec<Payment<N>>) {
+    let mut payments = vec![];
+    for out in burns {
+      let OutInstructionWithBalance { instruction: OutInstruction { address, data }, balance } =
+        out;
+      assert_eq!(balance.coin.network(), N::NETWORK);
+
+      if let Ok(address) = N::Address::try_from(address.consume()) {
+        // TODO: Add coin to payment
+        payments.push(Payment {
+          address,
+          data: data.map(|data| data.consume()),
+          amount: balance.amount.0,
+        });
+      }
+    }
+
+    let payments = payments;
+    match step {
+      RotationStep::UseExisting | RotationStep::NewAsChange => (payments, vec![]),
+      RotationStep::ForwardFromExisting | RotationStep::ClosingExisting => {
+        // Consume any payments the prior scheduler was unable to complete
+        // This should only actually matter once
+        let mut new_payments = self.existing.as_mut().unwrap().scheduler.consume_payments::<D>(txn);
+        // Add the new payments
+        new_payments.extend(payments);
+        (vec![], new_payments)
+      }
+    }
+  }
+
+  fn split_outputs_by_key(&self, outputs: Vec<N::Output>) -> (Vec<N::Output>, Vec<N::Output>) {
+    let mut existing_outputs = Vec::with_capacity(outputs.len());
+    let mut new_outputs = vec![];
+
+    let existing_key = self.existing.as_ref().unwrap().key;
+    let new_key = self.new.as_ref().map(|new| new.key);
+    for output in outputs {
+      if output.key() == existing_key {
+        existing_outputs.push(output);
+      } else {
+        assert_eq!(Some(output.key()), new_key);
+        new_outputs.push(output);
+      }
+    }
+
+    (existing_outputs, new_outputs)
+  }
+
+  // Manually creates Plans for all External outputs needing forwarding/refunding.
+  //
+  // Returns created Plans and a map of forwarded output IDs to their associated InInstructions.
+  fn filter_outputs_due_to_forwarding(
+    &self,
+    existing_outputs: &mut Vec<N::Output>,
+  ) -> (Vec<Plan<N>>, HashMap<Vec<u8>, InInstructionWithBalance>) {
+    // Manually create a Plan for all External outputs needing forwarding/refunding
+
+    /*
+      Sending a Plan, with arbitrary data proxying the InInstruction, would require adding
+      a flow for networks which drop their data to still embed arbitrary data. It'd also have
+      edge cases causing failures.
+
+      Instead, we save the InInstruction as we scan this output. Then, when the output is
+      successfully forwarded, we simply read it from the local database. This also saves the
+      costs of embedding arbitrary data.
+
+      Since we can't rely on the Eventuality system to detect if it's a forwarded transaction,
+      due to the asynchonicity of the Eventuality system, we instead interpret an External
+      output with no InInstruction, which has an amount associated with an InInstruction
+      being forwarded, as having been forwarded. This does create a specific edge case where
+      a user who doesn't include an InInstruction may not be refunded however, if they share
+      an exact amount with an expected-to-be-forwarded transaction. This is deemed acceptable.
+
+      TODO: Add a fourth address, forwarded_address, to prevent this.
+    */
+
+    let mut plans = vec![];
+    let mut forwarding = HashMap::new();
+    existing_outputs.retain(|output| {
+      if output.kind() == OutputType::External {
+        if let Some(instruction) = instruction_from_output::<N>(output) {
+          // Build a dedicated Plan forwarding this
+          plans.push(Plan {
+            key: self.existing.as_ref().unwrap().key,
+            inputs: vec![output.clone()],
+            payments: vec![],
+            change: Some(N::address(self.new.as_ref().unwrap().key)),
+          });
+
+          // Set the instruction for this output to be returned
+          forwarding.insert(output.id().as_ref().to_vec(), instruction);
+        }
+
+        // TODO: Refund here
+        false
+      } else {
+        true
+      }
+    });
+    (plans, forwarding)
+  }
+
+  // Filter newly received outputs due to the step being RotationStep::ClosingExisting.
+  fn filter_outputs_due_to_closing(
+    &mut self,
+    txn: &mut D::Transaction<'_>,
+    existing_outputs: &mut Vec<N::Output>,
+  ) -> Vec<Plan<N>> {
+    /*
+      The document says to only handle outputs we created. We don't know what outputs we
+      created. We do have an ordered view of equivalent outputs however, and can assume the
+      first (and likely only) ones are the ones we created.
+
+      Accordingly, only handling outputs we created should be definable as only handling
+      outputs from the resolution of Eventualities.
+
+      This isn't feasible. It requires knowing what Eventualities were completed in this block,
+      when we handle this block, which we don't know without fully serialized scanning + Batch
+      publication.
+
+      Take the following scenario:
+      1) A network uses 10 confirmations. Block x is scanned, meaning x+9a exists.
+      2) 67% of nodes process x, create, sign, and publish a TX, creating an Eventuality.
+      3) A reorganization to a shorter chain occurs, including the published TX in x+1b.
+      4) The 33% of nodes which are latent will be allowed to scan x+1b as soon as x+10b
+         exists. They won't wait for Serai to include the Batch for x until they try to scan
+         x+10b.
+      5) These latent nodes will handle x+1b, post-create an Eventuality, post-learn x+1b
+         contained resolutions, changing how x+1b should've been interpreted.
+
+      We either have to:
+      A) Fully serialize scanning (removing the ability to utilize throughput to allow higher
+         latency, at least while the step is `ClosingExisting`).
+      B) Create Eventualities immediately, which we can't do as then both the external
+         network's clock AND Serai's clock can trigger Eventualities, removing ordering.
+         We'd need to shift entirely to the external network's clock, only handling Burns
+         outside the parallelization window (which would be extremely latent).
+      C) Use a different mechanism to determine if we created an output.
+      D) Re-define which outputs are still to be handled after the 6 hour period expires, such
+         that the multisig's lifetime cannot be further extended yet it does fulfill its
+         responsibility.
+
+      External outputs to the existing multisig will be:
+      - Scanned before the rotation and unused (as used External outputs become Change)
+      - Forwarded immediately upon scanning
+      - Not scanned before the cut off time (and accordingly dropped)
+
+      For the first case, since they're scanned before the rotation and unused, they'll be
+      forwarded with all other available outputs (since they'll be available when scanned).
+
+      Change outputs will be:
+      - Scanned before the rotation and forwarded with all other available outputs
+      - Forwarded immediately upon scanning
+      - Not scanned before the cut off time, requiring an extension exclusive to these outputs
+
+      The important thing to note about honest Change outputs to the existing multisig is that
+      they'll only be created within `CONFIRMATIONS+1` blocks of the activation block. Also
+      important to note is that there's another explicit window of `CONFIRMATIONS` before the
+      6 hour window.
+
+      Eventualities are not guaranteed to be known before we scan the block containing their
+      resolution. They are guaranteed to be known within `CONFIRMATIONS-1` blocks however, due
+      to the limitation on how far we'll scan ahead.
+
+      This means we will know of all Eventualities related to Change outputs we need to forward
+      before the 6 hour period begins (as forwarding outputs will not create any Change outputs
+      to the existing multisig).
+
+      This means a definition of complete can be defined as:
+      1) Handled all Branch outputs
+      2) Forwarded all External outputs received before the end of 6 hour window
+      3) Forwarded the results of all Eventualities with Change, which will have been created
+         before the 6 hour window
+
+      How can we track and ensure this without needing to check if an output is from the
+      resolution of an Eventuality?
+
+      1) We only create Branch outputs before the 6 hour window starts. These are guaranteed
+         to appear within `CONFIRMATIONS` blocks. They will exist with arbitrary depth however,
+         meaning that upon completion they will spawn several more Eventualities. The further
+         created Eventualities re-risk being present after the 6 hour period ends.
+
+         We can:
+         1) Build a queue for Branch outputs, delaying their handling until relevant
+            Eventualities are guaranteed to be present.
+
+            This solution would theoretically work for all outputs and allow collapsing this
+            problem to simply:
+
+            > Accordingly, only handling outputs we created should be definable as only
+              handling outputs from the resolution of Eventualities.
+
+         2) Create all Eventualities under a Branch at time of Branch creation.
+            This idea fails as Plans are tightly bound to outputs.
+
+         3) Don't track Branch outputs by Eventualities, yet by the amount of Branch outputs
+            remaining. Any Branch output received, of a useful amount, is assumed to be our
+            own and handled. All other Branch outputs, even if they're the completion of some
+            Eventuality, are dropped.
+
+            This avoids needing any additional queue, avoiding additional pipelining/latency.
+
+      2) External outputs are self-evident. We simply stop handling them at the cut-off point,
+         and only start checking after `CONFIRMATIONS` blocks if all Eventualities are
+         complete.
+
+      3) Since all Change Eventualities will be known prior to the 6 hour window's beginning,
+         we can safely check if a received Change output is the resolution of an Eventuality.
+         We only need to forward it if so. Forwarding it simply requires only checking if
+         Eventualities are complete after `CONFIRMATIONS` blocks, same as for straggling
+         External outputs.
+    */
+
+    let mut plans = vec![];
+    existing_outputs.retain(|output| {
+      match output.kind() {
+        OutputType::External => false,
+        OutputType::Branch => {
+          let scheduler = &mut self.existing.as_mut().unwrap().scheduler;
+          // There *would* be a race condition here due to the fact we only mark a `Branch` output
+          // as needed when we process the block (and handle scheduling), yet actual `Branch`
+          // outputs may appear as soon as the next block (and we scan the next block before we
+          // process the prior block)
+          //
+          // Unlike Eventuality checking, which happens on scanning and is therefore asynchronous,
+          // all scheduling (and this check against the scheduler) happens on processing, which is
+          // synchronous
+          //
+          // While we could move Eventuality checking into the block processing, removing its
+          // asynchonicity, we could only check data the Scanner deems important. The Scanner won't
+          // deem important Eventuality resolutions which don't create an output to Serai unless
+          // it knows of the Eventuality. Accordingly, at best we could have a split role (the
+          // Scanner noting completion of Eventualities which don't have relevant outputs, the
+          // processing noting completion of ones which do)
+          //
+          // This is unnecessary, due to the current flow around Eventuality resolutions and the
+          // current bounds naturally found being sufficiently amenable, yet notable for the future
+          if scheduler.can_use_branch(output.amount()) {
+            // We could simply call can_use_branch, yet it'd have an edge case where if we receive
+            // two outputs for 100, and we could use one such output, we'd handle both.
+            //
+            // Individually schedule each output once confirming they're usable in order to avoid
+            // this.
+            let mut plan = scheduler.schedule::<D>(
+              txn,
+              vec![output.clone()],
+              vec![],
+              self.new.as_ref().unwrap().key,
+              false,
+            );
+            assert_eq!(plan.len(), 1);
+            let plan = plan.remove(0);
+            plans.push(plan);
+          }
+          false
+        }
+        OutputType::Change => {
+          // If the TX containing this output resolved an Eventuality...
+          if let Some(plan) = MultisigsDb::<N, D>::resolved_plan(txn, output.tx_id()) {
+            // And the Eventuality had change...
+            // We need this check as Eventualities have a race condition and can't be relied
+            // on, as extensively detailed above. Eventualities explicitly with change do have
+            // a safe timing window however
+            if MultisigsDb::<N, D>::plan_by_key_with_self_change(
+              txn,
+              // Pass the key so the DB checks the Plan's key is this multisig's, preventing a
+              // potential issue where the new multisig creates a Plan with change *and a
+              // payment to the existing multisig's change address*
+              self.existing.as_ref().unwrap().key,
+              plan,
+            ) {
+              // Then this is an honest change output we need to forward
+              // (or it's a payment to the change address in the same transaction as an honest
+              // change output, which is fine to let slip in)
+              return true;
+            }
+          }
+          false
+        }
+      }
+    });
+    plans
+  }
+
+  // Returns the Plans caused from a block being acknowledged.
+  //
+  // Will rotate keys if the block acknowledged is the retirement block.
+  async fn plans_from_block(
+    &mut self,
+    txn: &mut D::Transaction<'_>,
+    block_number: usize,
+    block_id: <N::Block as Block<N>>::Id,
+    step: &mut RotationStep,
+    burns: Vec<OutInstructionWithBalance>,
+  ) -> (bool, Vec<Plan<N>>, HashMap<Vec<u8>, InInstructionWithBalance>) {
+    let (mut existing_payments, mut new_payments) = self.burns_to_payments(txn, *step, burns);
+
+    // We now have to acknowledge the acknowledged block, if it's new
+    // It won't be if this block's `InInstruction`s were split into multiple `Batch`s
+    let (acquired_lock, (mut existing_outputs, new_outputs)) = {
+      let (acquired_lock, outputs) = if ScannerHandle::<N, D>::db_scanned(txn)
+        .expect("published a Batch despite never scanning a block") <
+        block_number
+      {
+        let (is_retirement_block, outputs) = self.scanner.ack_block(txn, block_id.clone()).await;
+        if is_retirement_block {
+          let existing = self.existing.take().unwrap();
+          assert!(existing.scheduler.empty());
+          self.existing = self.new.take();
+          *step = RotationStep::UseExisting;
+          assert!(existing_payments.is_empty());
+          existing_payments = new_payments;
+          new_payments = vec![];
+        }
+        (true, outputs)
+      } else {
+        (false, vec![])
+      };
+      (acquired_lock, self.split_outputs_by_key(outputs))
+    };
+
+    let (mut plans, forwarded_external_outputs) = match *step {
+      RotationStep::UseExisting | RotationStep::NewAsChange => (vec![], HashMap::new()),
+      RotationStep::ForwardFromExisting => {
+        self.filter_outputs_due_to_forwarding(&mut existing_outputs)
+      }
+      RotationStep::ClosingExisting => {
+        (self.filter_outputs_due_to_closing(txn, &mut existing_outputs), HashMap::new())
+      }
+    };
+
+    plans.extend({
+      let existing = self.existing.as_mut().unwrap();
+      let existing_key = existing.key;
+      self.existing.as_mut().unwrap().scheduler.schedule::<D>(
+        txn,
+        existing_outputs,
+        existing_payments,
+        match *step {
+          RotationStep::UseExisting => existing_key,
+          RotationStep::NewAsChange |
+          RotationStep::ForwardFromExisting |
+          RotationStep::ClosingExisting => self.new.as_ref().unwrap().key,
+        },
+        match *step {
+          RotationStep::UseExisting | RotationStep::NewAsChange => false,
+          RotationStep::ForwardFromExisting | RotationStep::ClosingExisting => true,
+        },
+      )
+    });
+
+    for plan in &plans {
+      assert_eq!(plan.key, self.existing.as_ref().unwrap().key);
+      if plan.change == Some(N::change_address(plan.key)) {
+        // Assert these are only created during the expected step
+        match *step {
+          RotationStep::UseExisting => {}
+          RotationStep::NewAsChange |
+          RotationStep::ForwardFromExisting |
+          RotationStep::ClosingExisting => panic!("change was set to self despite rotating"),
+        }
+      }
+    }
+
+    if let Some(new) = self.new.as_mut() {
+      plans.extend(new.scheduler.schedule::<D>(txn, new_outputs, new_payments, new.key, false));
+    }
+
+    (acquired_lock, plans, forwarded_external_outputs)
+  }
+
+  /// Handle a SubstrateBlock event, building the relevant Plans.
+  pub async fn substrate_block(
+    &mut self,
+    txn: &mut D::Transaction<'_>,
+    network: &N,
+    context: SubstrateContext,
+    burns: Vec<OutInstructionWithBalance>,
+  ) -> (bool, Vec<(<N::Curve as Ciphersuite>::G, [u8; 32], N::SignableTransaction, N::Eventuality)>)
+  {
+    let mut block_id = <N::Block as Block<N>>::Id::default();
+    block_id.as_mut().copy_from_slice(context.network_latest_finalized_block.as_ref());
+    let block_number = ScannerHandle::<N, D>::block_number(txn, &block_id)
+      .expect("SubstrateBlock with context we haven't synced");
+
+    // Determine what step of rotation we're currently in
+    let mut step = self.current_rotation_step(block_number);
+
+    // Get the Plans from this block
+    let (acquired_lock, plans, mut forwarded_external_outputs) =
+      self.plans_from_block(txn, block_number, block_id, &mut step, burns).await;
+
+    let res = {
+      let mut res = Vec::with_capacity(plans.len());
+      let fee = get_fee(network, block_number).await;
+
+      for plan in plans {
+        let id = plan.id();
+        info!("preparing plan {}: {:?}", hex::encode(id), plan);
+
+        let key = plan.key;
+        let key_bytes = key.to_bytes();
+        MultisigsDb::<N, D>::save_active_plan(
+          txn,
+          key_bytes.as_ref(),
+          block_number.try_into().unwrap(),
+          &plan,
+        );
+
+        let to_be_forwarded = forwarded_external_outputs.remove(plan.inputs[0].id().as_ref());
+        if to_be_forwarded.is_some() {
+          assert_eq!(plan.inputs.len(), 1);
+        }
+        let (tx, branches) = prepare_send(network, block_number, fee, plan).await;
+
+        // If this is a Plan for an output we're forwarding, we need to save the InInstruction for
+        // its output under the amount successfully forwarded
+        if let Some(mut instruction) = to_be_forwarded {
+          // If we can't successfully create a forwarding TX, simply drop this
+          if let Some(tx) = &tx {
+            instruction.balance.amount.0 -= tx.0.fee();
+            MultisigsDb::<N, D>::save_forwarded_output(txn, instruction);
+          }
+        }
+
+        for branch in branches {
+          let existing = self.existing.as_mut().unwrap();
+          let to_use = if key == existing.key {
+            existing
+          } else {
+            let new = self
+              .new
+              .as_mut()
+              .expect("plan wasn't for existing multisig yet there wasn't a new multisig");
+            assert_eq!(key, new.key);
+            new
+          };
+
+          to_use.scheduler.created_output::<D>(txn, branch.expected, branch.actual);
+        }
+
+        if let Some((tx, eventuality)) = tx {
+          // The main function we return to will send an event to the coordinator which must be
+          // fired before these registered Eventualities have their Completions fired
+          // Safety is derived from a mutable lock on the Scanner being preserved, preventing
+          // scanning (and detection of Eventuality resolutions) before it's released
+          // It's only released by the main function after it does what it will
+          self
+            .scanner
+            .register_eventuality(key_bytes.as_ref(), block_number, id, eventuality.clone())
+            .await;
+
+          res.push((key, id, tx, eventuality));
+        }
+
+        // TODO: If the TX is None, restore its inputs to the scheduler
+        // Otherwise, if the TX had a change output, dropping its inputs would burn funds
+        // Are there exceptional cases upon rotation?
+      }
+      res
+    };
+    (acquired_lock, res)
+  }
+
+  pub async fn release_scanner_lock(&mut self) {
+    self.scanner.release_lock().await;
+  }
+
+  fn scanner_event_to_multisig_event(
+    &self,
+    txn: &mut D::Transaction<'_>,
+    msg: ScannerEvent<N>,
+  ) -> MultisigEvent<N> {
+    let (block_number, event) = match msg {
+      ScannerEvent::Block { is_retirement_block, block, outputs } => {
+        // Since the Scanner is asynchronous, the following is a concern for race conditions
+        // We safely know the step of a block since keys are declared, and the Scanner is safe
+        // with respect to the declaration of keys
+        // Accordingly, the following calls regarding new keys and step should be safe
+        let block_number = ScannerHandle::<N, D>::block_number(txn, &block)
+          .expect("didn't have the block number for a block we just scanned");
+        let step = self.current_rotation_step(block_number);
+
+        let mut instructions = vec![];
+        for output in outputs {
+          // If these aren't externally received funds, don't handle it as an instruction
+          if output.kind() != OutputType::External {
+            continue;
+          }
+
+          // If this is an External transaction to the existing multisig, and we're either solely
+          // forwarding or closing the existing multisig, drop it
+          // In the case of the forwarding case, we'll report it once it hits the new multisig
+          if (match step {
+            RotationStep::UseExisting | RotationStep::NewAsChange => false,
+            RotationStep::ForwardFromExisting | RotationStep::ClosingExisting => true,
+          }) && (output.key() == self.existing.as_ref().unwrap().key)
+          {
+            continue;
+          }
+
+          let instruction = if let Some(instruction) = instruction_from_output::<N>(&output) {
+            instruction
+          } else {
+            if !output.data().is_empty() {
+              // TODO2: Refund
+              continue;
+            }
+
+            if let Some(instruction) =
+              MultisigsDb::<N, D>::take_forwarded_output(txn, output.amount())
+            {
+              instruction
+            } else {
+              // TODO2: Refund
+              continue;
+            }
+          };
+
+          // Delay External outputs received to new multisig earlier than expected
+          if Some(output.key()) == self.new.as_ref().map(|new| new.key) {
+            match step {
+              RotationStep::UseExisting => {
+                MultisigsDb::<N, D>::save_delayed_output(txn, instruction);
+                continue;
+              }
+              RotationStep::NewAsChange |
+              RotationStep::ForwardFromExisting |
+              RotationStep::ClosingExisting => {}
+            }
+          }
+
+          instructions.push(instruction);
+        }
+
+        // If any outputs were delayed, append them into this block
+        match step {
+          RotationStep::UseExisting => {}
+          RotationStep::NewAsChange |
+          RotationStep::ForwardFromExisting |
+          RotationStep::ClosingExisting => {
+            instructions.extend(MultisigsDb::<N, D>::take_delayed_outputs(txn));
+          }
+        }
+
+        let mut block_hash = [0; 32];
+        block_hash.copy_from_slice(block.as_ref());
+        let mut batch_id = MultisigsDb::<N, D>::next_batch_id(txn);
+
+        // start with empty batch
+        let mut batches = vec![Batch {
+          network: N::NETWORK,
+          id: batch_id,
+          block: BlockHash(block_hash),
+          instructions: vec![],
+        }];
+
+        for instruction in instructions {
+          let batch = batches.last_mut().unwrap();
+          batch.instructions.push(instruction);
+
+          // check if batch is over-size
+          if batch.encode().len() > MAX_BATCH_SIZE {
+            // pop the last instruction so it's back in size
+            let instruction = batch.instructions.pop().unwrap();
+
+            // bump the id for the new batch
+            batch_id += 1;
+
+            // make a new batch with this instruction included
+            batches.push(Batch {
+              network: N::NETWORK,
+              id: batch_id,
+              block: BlockHash(block_hash),
+              instructions: vec![instruction],
+            });
+          }
+        }
+
+        // Save the next batch ID
+        MultisigsDb::<N, D>::set_next_batch_id(txn, batch_id + 1);
+
+        (
+          block_number,
+          MultisigEvent::Batches(
+            if is_retirement_block {
+              Some((self.existing.as_ref().unwrap().key, self.new.as_ref().unwrap().key))
+            } else {
+              None
+            },
+            batches,
+          ),
+        )
+      }
+
+      // This must be emitted before ScannerEvent::Block for all completions of known Eventualities
+      // within the block. Unknown Eventualities may have their Completed events emitted after
+      // ScannerEvent::Block however.
+      ScannerEvent::Completed(key, block_number, id, tx) => {
+        MultisigsDb::<N, D>::resolve_plan(txn, &key, id, tx.id());
+        (block_number, MultisigEvent::Completed(key, id, tx))
+      }
+    };
+
+    // If we either received a Block event (which will be the trigger when we have no
+    // Plans/Eventualities leading into ClosingExisting), or we received the last Completed for
+    // this multisig, set its retirement block
+    let existing = self.existing.as_ref().unwrap();
+
+    // This multisig is closing
+    let closing = self.current_rotation_step(block_number) == RotationStep::ClosingExisting;
+    // There's nothing left in its Scheduler. This call is safe as:
+    // 1) When ClosingExisting, all outputs should've been already forwarded, preventing
+    //    new UTXOs from accumulating.
+    // 2) No new payments should be issued.
+    // 3) While there may be plans, they'll be dropped to create Eventualities.
+    //    If this Eventuality is resolved, the Plan has already been dropped.
+    // 4) If this Eventuality will trigger a Plan, it'll still be in the plans HashMap.
+    let scheduler_is_empty = closing && existing.scheduler.empty();
+    // Nothing is still being signed
+    let no_active_plans = scheduler_is_empty &&
+      MultisigsDb::<N, D>::active_plans(txn, existing.key.to_bytes().as_ref()).is_empty();
+
+    self
+      .scanner
+      .multisig_completed
+      // The above explicitly included their predecessor to ensure short-circuiting, yet their
+      // names aren't defined as an aggregate check. Still including all three here ensures all are
+      // used in the final value
+      .send(closing && scheduler_is_empty && no_active_plans)
+      .unwrap();
+
+    event
+  }
+
+  // async fn where dropping the Future causes no state changes
+  // This property is derived from recv having this property, and recv being the only async call
+  pub async fn next_event(&mut self, txn: &RwLock<D::Transaction<'_>>) -> MultisigEvent<N> {
+    let event = self.scanner.events.recv().await.unwrap();
+
+    // No further code is async
+
+    self.scanner_event_to_multisig_event(&mut *txn.write().unwrap(), event)
+  }
+}

processor/src/multisigs/scanner.rs

@@ -0,0 +1,727 @@
+use core::marker::PhantomData;
+use std::{
+  sync::Arc,
+  io::Read,
+  time::Duration,
+  collections::{VecDeque, HashSet, HashMap},
+};
+
+use ciphersuite::group::GroupEncoding;
+use frost::curve::Ciphersuite;
+
+use log::{info, debug, warn};
+use tokio::{
+  sync::{RwLockReadGuard, RwLockWriteGuard, RwLock, mpsc},
+  time::sleep,
+};
+
+use crate::{
+  Get, DbTxn, Db,
+  networks::{Output, Transaction, EventualitiesTracker, Block, Network},
+};
+
+#[derive(Clone, Debug)]
+pub enum ScannerEvent<N: Network> {
+  // Block scanned
+  Block { is_retirement_block: bool, block: <N::Block as Block<N>>::Id, outputs: Vec<N::Output> },
+  // Eventuality completion found on-chain
+  Completed(Vec<u8>, usize, [u8; 32], N::Transaction),
+}
+
+pub type ScannerEventChannel<N> = mpsc::UnboundedReceiver<ScannerEvent<N>>;
+
+#[derive(Clone, Debug)]
+struct ScannerDb<N: Network, D: Db>(PhantomData<N>, PhantomData<D>);
+impl<N: Network, D: Db> ScannerDb<N, D> {
+  fn scanner_key(dst: &'static [u8], key: impl AsRef<[u8]>) -> Vec<u8> {
+    D::key(b"SCANNER", dst, key)
+  }
+
+  fn block_key(number: usize) -> Vec<u8> {
+    Self::scanner_key(b"block_id", u64::try_from(number).unwrap().to_le_bytes())
+  }
+  fn block_number_key(id: &<N::Block as Block<N>>::Id) -> Vec<u8> {
+    Self::scanner_key(b"block_number", id)
+  }
+  fn save_block(txn: &mut D::Transaction<'_>, number: usize, id: &<N::Block as Block<N>>::Id) {
+    txn.put(Self::block_number_key(id), u64::try_from(number).unwrap().to_le_bytes());
+    txn.put(Self::block_key(number), id);
+  }
+  fn block<G: Get>(getter: &G, number: usize) -> Option<<N::Block as Block<N>>::Id> {
+    getter.get(Self::block_key(number)).map(|id| {
+      let mut res = <N::Block as Block<N>>::Id::default();
+      res.as_mut().copy_from_slice(&id);
+      res
+    })
+  }
+  fn block_number<G: Get>(getter: &G, id: &<N::Block as Block<N>>::Id) -> Option<usize> {
+    getter
+      .get(Self::block_number_key(id))
+      .map(|number| u64::from_le_bytes(number.try_into().unwrap()).try_into().unwrap())
+  }
+
+  fn keys_key() -> Vec<u8> {
+    Self::scanner_key(b"keys", b"")
+  }
+  fn register_key(
+    txn: &mut D::Transaction<'_>,
+    activation_number: usize,
+    key: <N::Curve as Ciphersuite>::G,
+  ) {
+    let mut keys = txn.get(Self::keys_key()).unwrap_or(vec![]);
+
+    let key_bytes = key.to_bytes();
+
+    let key_len = key_bytes.as_ref().len();
+    assert_eq!(keys.len() % (8 + key_len), 0);
+
+    // Sanity check this key isn't already present
+    let mut i = 0;
+    while i < keys.len() {
+      if &keys[(i + 8) .. ((i + 8) + key_len)] == key_bytes.as_ref() {
+        panic!("adding {} as a key yet it was already present", hex::encode(key_bytes));
+      }
+      i += 8 + key_len;
+    }
+
+    keys.extend(u64::try_from(activation_number).unwrap().to_le_bytes());
+    keys.extend(key_bytes.as_ref());
+    txn.put(Self::keys_key(), keys);
+  }
+  fn keys<G: Get>(getter: &G) -> Vec<(usize, <N::Curve as Ciphersuite>::G)> {
+    let bytes_vec = getter.get(Self::keys_key()).unwrap_or(vec![]);
+    let mut bytes: &[u8] = bytes_vec.as_ref();
+
+    // Assumes keys will be 32 bytes when calculating the capacity
+    // If keys are larger, this may allocate more memory than needed
+    // If keys are smaller, this may require additional allocations
+    // Either are fine
+    let mut res = Vec::with_capacity(bytes.len() / (8 + 32));
+    while !bytes.is_empty() {
+      let mut activation_number = [0; 8];
+      bytes.read_exact(&mut activation_number).unwrap();
+      let activation_number = u64::from_le_bytes(activation_number).try_into().unwrap();
+
+      res.push((activation_number, N::Curve::read_G(&mut bytes).unwrap()));
+    }
+    res
+  }
+  fn retire_key(txn: &mut D::Transaction<'_>) {
+    let keys = Self::keys(txn);
+    assert_eq!(keys.len(), 2);
+    txn.del(Self::keys_key());
+    Self::register_key(txn, keys[1].0, keys[1].1);
+  }
+
+  fn seen_key(id: &<N::Output as Output<N>>::Id) -> Vec<u8> {
+    Self::scanner_key(b"seen", id)
+  }
+  fn seen<G: Get>(getter: &G, id: &<N::Output as Output<N>>::Id) -> bool {
+    getter.get(Self::seen_key(id)).is_some()
+  }
+
+  fn outputs_key(block: &<N::Block as Block<N>>::Id) -> Vec<u8> {
+    Self::scanner_key(b"outputs", block.as_ref())
+  }
+  fn save_outputs(
+    txn: &mut D::Transaction<'_>,
+    block: &<N::Block as Block<N>>::Id,
+    outputs: &[N::Output],
+  ) {
+    let mut bytes = Vec::with_capacity(outputs.len() * 64);
+    for output in outputs {
+      output.write(&mut bytes).unwrap();
+    }
+    txn.put(Self::outputs_key(block), bytes);
+  }
+  fn outputs(
+    txn: &D::Transaction<'_>,
+    block: &<N::Block as Block<N>>::Id,
+  ) -> Option<Vec<N::Output>> {
+    let bytes_vec = txn.get(Self::outputs_key(block))?;
+    let mut bytes: &[u8] = bytes_vec.as_ref();
+
+    let mut res = vec![];
+    while !bytes.is_empty() {
+      res.push(N::Output::read(&mut bytes).unwrap());
+    }
+    Some(res)
+  }
+
+  fn scanned_block_key() -> Vec<u8> {
+    Self::scanner_key(b"scanned_block", [])
+  }
+
+  fn save_scanned_block(txn: &mut D::Transaction<'_>, block: usize) -> Vec<N::Output> {
+    let id = Self::block(txn, block); // It may be None for the first key rotated to
+    let outputs =
+      if let Some(id) = id.as_ref() { Self::outputs(txn, id).unwrap_or(vec![]) } else { vec![] };
+
+    // Mark all the outputs from this block as seen
+    for output in &outputs {
+      txn.put(Self::seen_key(&output.id()), b"");
+    }
+
+    txn.put(Self::scanned_block_key(), u64::try_from(block).unwrap().to_le_bytes());
+
+    // Return this block's outputs so they can be pruned from the RAM cache
+    outputs
+  }
+  fn latest_scanned_block<G: Get>(getter: &G) -> Option<usize> {
+    getter
+      .get(Self::scanned_block_key())
+      .map(|bytes| u64::from_le_bytes(bytes.try_into().unwrap()).try_into().unwrap())
+  }
+
+  fn retirement_block_key(key: &<N::Curve as Ciphersuite>::G) -> Vec<u8> {
+    Self::scanner_key(b"retirement_block", key.to_bytes())
+  }
+  fn save_retirement_block(
+    txn: &mut D::Transaction<'_>,
+    key: &<N::Curve as Ciphersuite>::G,
+    block: usize,
+  ) {
+    txn.put(Self::retirement_block_key(key), u64::try_from(block).unwrap().to_le_bytes());
+  }
+  fn retirement_block<G: Get>(getter: &G, key: &<N::Curve as Ciphersuite>::G) -> Option<usize> {
+    getter
+      .get(Self::retirement_block_key(key))
+      .map(|bytes| usize::try_from(u64::from_le_bytes(bytes.try_into().unwrap())).unwrap())
+  }
+}
+
+/// The Scanner emits events relating to the blockchain, notably received outputs.
+///
+/// It WILL NOT fail to emit an event, even if it reboots at selected moments.
+///
+/// It MAY fire the same event multiple times.
+#[derive(Debug)]
+pub struct Scanner<N: Network, D: Db> {
+  _db: PhantomData<D>,
+
+  keys: Vec<(usize, <N::Curve as Ciphersuite>::G)>,
+
+  eventualities: HashMap<Vec<u8>, EventualitiesTracker<N::Eventuality>>,
+
+  ram_scanned: Option<usize>,
+  ram_outputs: HashSet<Vec<u8>>,
+
+  need_ack: VecDeque<usize>,
+
+  events: mpsc::UnboundedSender<ScannerEvent<N>>,
+}
+
+#[derive(Clone, Debug)]
+struct ScannerHold<N: Network, D: Db> {
+  scanner: Arc<RwLock<Option<Scanner<N, D>>>>,
+}
+impl<N: Network, D: Db> ScannerHold<N, D> {
+  async fn read(&self) -> RwLockReadGuard<'_, Option<Scanner<N, D>>> {
+    loop {
+      let lock = self.scanner.read().await;
+      if lock.is_none() {
+        drop(lock);
+        tokio::task::yield_now().await;
+        continue;
+      }
+      return lock;
+    }
+  }
+  async fn write(&self) -> RwLockWriteGuard<'_, Option<Scanner<N, D>>> {
+    loop {
+      let lock = self.scanner.write().await;
+      if lock.is_none() {
+        drop(lock);
+        tokio::task::yield_now().await;
+        continue;
+      }
+      return lock;
+    }
+  }
+  // This is safe to not check if something else already acquired the Scanner as the only caller is
+  // sequential.
+  async fn long_term_acquire(&self) -> Scanner<N, D> {
+    self.scanner.write().await.take().unwrap()
+  }
+  async fn restore(&self, scanner: Scanner<N, D>) {
+    let _ = self.scanner.write().await.insert(scanner);
+  }
+}
+
+#[derive(Debug)]
+pub struct ScannerHandle<N: Network, D: Db> {
+  scanner: ScannerHold<N, D>,
+  held_scanner: Option<Scanner<N, D>>,
+  pub events: ScannerEventChannel<N>,
+  pub multisig_completed: mpsc::UnboundedSender<bool>,
+}
+
+impl<N: Network, D: Db> ScannerHandle<N, D> {
+  pub async fn ram_scanned(&self) -> usize {
+    self.scanner.read().await.as_ref().unwrap().ram_scanned.unwrap_or(0)
+  }
+
+  /// Register a key to scan for.
+  pub async fn register_key(
+    &mut self,
+    txn: &mut D::Transaction<'_>,
+    activation_number: usize,
+    key: <N::Curve as Ciphersuite>::G,
+  ) {
+    let mut scanner_lock = self.scanner.write().await;
+    let scanner = scanner_lock.as_mut().unwrap();
+    assert!(
+      activation_number > scanner.ram_scanned.unwrap_or(0),
+      "activation block of new keys was already scanned",
+    );
+
+    info!("Registering key {} in scanner at {activation_number}", hex::encode(key.to_bytes()));
+
+    if scanner.keys.is_empty() {
+      assert!(scanner.ram_scanned.is_none());
+      scanner.ram_scanned = Some(activation_number);
+      assert!(ScannerDb::<N, D>::save_scanned_block(txn, activation_number).is_empty());
+    }
+
+    ScannerDb::<N, D>::register_key(txn, activation_number, key);
+    scanner.keys.push((activation_number, key));
+    #[cfg(not(test))] // TODO: A test violates this. Improve the test with a better flow
+    assert!(scanner.keys.len() <= 2);
+
+    scanner.eventualities.insert(key.to_bytes().as_ref().to_vec(), EventualitiesTracker::new());
+  }
+
+  pub fn db_scanned<G: Get>(getter: &G) -> Option<usize> {
+    ScannerDb::<N, D>::latest_scanned_block(getter)
+  }
+
+  // This perform a database read which isn't safe with regards to if the value is set or not
+  // It may be set, when it isn't expected to be set, or not set, when it is expected to be set
+  // Since the value is static, if it's set, it's correctly set
+  pub fn block_number<G: Get>(getter: &G, id: &<N::Block as Block<N>>::Id) -> Option<usize> {
+    ScannerDb::<N, D>::block_number(getter, id)
+  }
+
+  /// Acknowledge having handled a block.
+  ///
+  /// Creates a lock over the Scanner, preventing its independent scanning operations until
+  /// released.
+  ///
+  /// This must only be called on blocks which have been scanned in-memory.
+  pub async fn ack_block(
+    &mut self,
+    txn: &mut D::Transaction<'_>,
+    id: <N::Block as Block<N>>::Id,
+  ) -> (bool, Vec<N::Output>) {
+    debug!("block {} acknowledged", hex::encode(&id));
+
+    let mut scanner = self.scanner.long_term_acquire().await;
+
+    // Get the number for this block
+    let number = ScannerDb::<N, D>::block_number(txn, &id)
+      .expect("main loop trying to operate on data we haven't scanned");
+    log::trace!("block {} was {number}", hex::encode(&id));
+
+    let outputs = ScannerDb::<N, D>::save_scanned_block(txn, number);
+    // This has a race condition if we try to ack a block we scanned on a prior boot, and we have
+    // yet to scan it on this boot
+    assert!(number <= scanner.ram_scanned.unwrap());
+    for output in &outputs {
+      assert!(scanner.ram_outputs.remove(output.id().as_ref()));
+    }
+
+    assert_eq!(scanner.need_ack.pop_front().unwrap(), number);
+
+    self.held_scanner = Some(scanner);
+
+    // Load the key from the DB, as it will have already been removed from RAM if retired
+    let key = ScannerDb::<N, D>::keys(txn)[0].1;
+    let is_retirement_block = ScannerDb::<N, D>::retirement_block(txn, &key) == Some(number);
+    if is_retirement_block {
+      ScannerDb::<N, D>::retire_key(txn);
+    }
+    (is_retirement_block, outputs)
+  }
+
+  pub async fn register_eventuality(
+    &mut self,
+    key: &[u8],
+    block_number: usize,
+    id: [u8; 32],
+    eventuality: N::Eventuality,
+  ) {
+    let mut lock;
+    // We won't use held_scanner if we're re-registering on boot
+    (if let Some(scanner) = self.held_scanner.as_mut() {
+      scanner
+    } else {
+      lock = Some(self.scanner.write().await);
+      lock.as_mut().unwrap().as_mut().unwrap()
+    })
+    .eventualities
+    .get_mut(key)
+    .unwrap()
+    .register(block_number, id, eventuality)
+  }
+
+  pub async fn release_lock(&mut self) {
+    self.scanner.restore(self.held_scanner.take().unwrap()).await
+  }
+}
+
+impl<N: Network, D: Db> Scanner<N, D> {
+  #[allow(clippy::type_complexity, clippy::new_ret_no_self)]
+  pub fn new(
+    network: N,
+    db: D,
+  ) -> (ScannerHandle<N, D>, Vec<(usize, <N::Curve as Ciphersuite>::G)>) {
+    let (events_send, events_recv) = mpsc::unbounded_channel();
+    let (multisig_completed_send, multisig_completed_recv) = mpsc::unbounded_channel();
+
+    let keys = ScannerDb::<N, D>::keys(&db);
+    let mut eventualities = HashMap::new();
+    for key in &keys {
+      eventualities.insert(key.1.to_bytes().as_ref().to_vec(), EventualitiesTracker::new());
+    }
+
+    let ram_scanned = ScannerDb::<N, D>::latest_scanned_block(&db);
+
+    let scanner = ScannerHold {
+      scanner: Arc::new(RwLock::new(Some(Scanner {
+        _db: PhantomData,
+
+        keys: keys.clone(),
+
+        eventualities,
+
+        ram_scanned,
+        ram_outputs: HashSet::new(),
+
+        need_ack: VecDeque::new(),
+
+        events: events_send,
+      }))),
+    };
+    tokio::spawn(Scanner::run(db, network, scanner.clone(), multisig_completed_recv));
+
+    (
+      ScannerHandle {
+        scanner,
+        held_scanner: None,
+        events: events_recv,
+        multisig_completed: multisig_completed_send,
+      },
+      keys,
+    )
+  }
+
+  async fn emit(&mut self, event: ScannerEvent<N>) -> bool {
+    if self.events.send(event).is_err() {
+      info!("Scanner handler was dropped. Shutting down?");
+      return false;
+    }
+    true
+  }
+
+  // An async function, to be spawned on a task, to discover and report outputs
+  async fn run(
+    mut db: D,
+    network: N,
+    scanner_hold: ScannerHold<N, D>,
+    mut multisig_completed: mpsc::UnboundedReceiver<bool>,
+  ) {
+    loop {
+      let (ram_scanned, latest_block_to_scan) = {
+        // Sleep 5 seconds to prevent hammering the node/scanner lock
+        sleep(Duration::from_secs(5)).await;
+
+        let ram_scanned = {
+          let scanner_lock = scanner_hold.read().await;
+          let scanner = scanner_lock.as_ref().unwrap();
+
+          // If we're not scanning for keys yet, wait until we are
+          if scanner.keys.is_empty() {
+            continue;
+          }
+
+          let ram_scanned = scanner.ram_scanned.unwrap();
+          // If a Batch has taken too long to be published, start waiting until it is before
+          // continuing scanning
+          // Solves a race condition around multisig rotation, documented in the relevant doc
+          // and demonstrated with mini
+          if let Some(needing_ack) = scanner.need_ack.front() {
+            let next = ram_scanned + 1;
+            let limit = needing_ack + N::CONFIRMATIONS;
+            assert!(next <= limit);
+            if next == limit {
+              continue;
+            }
+          };
+
+          ram_scanned
+        };
+
+        (
+          ram_scanned,
+          loop {
+            break match network.get_latest_block_number().await {
+              // Only scan confirmed blocks, which we consider effectively finalized
+              // CONFIRMATIONS - 1 as whatever's in the latest block already has 1 confirm
+              Ok(latest) => latest.saturating_sub(N::CONFIRMATIONS.saturating_sub(1)),
+              Err(_) => {
+                warn!("couldn't get latest block number");
+                sleep(Duration::from_secs(60)).await;
+                continue;
+              }
+            };
+          },
+        )
+      };
+
+      for block_being_scanned in (ram_scanned + 1) ..= latest_block_to_scan {
+        // Redo the checks for if we're too far ahead
+        {
+          let needing_ack = {
+            let scanner_lock = scanner_hold.read().await;
+            let scanner = scanner_lock.as_ref().unwrap();
+            scanner.need_ack.front().cloned()
+          };
+
+          if let Some(needing_ack) = needing_ack {
+            let limit = needing_ack + N::CONFIRMATIONS;
+            assert!(block_being_scanned <= limit);
+            if block_being_scanned == limit {
+              break;
+            }
+          }
+        }
+
+        let block = match network.get_block(block_being_scanned).await {
+          Ok(block) => block,
+          Err(_) => {
+            warn!("couldn't get block {block_being_scanned}");
+            break;
+          }
+        };
+        let block_id = block.id();
+
+        info!("scanning block: {} ({block_being_scanned})", hex::encode(&block_id));
+
+        // These DB calls are safe, despite not having a txn, since they're static values
+        // There's no issue if they're written in advance of expected (such as on reboot)
+        // They're also only expected here
+        if let Some(id) = ScannerDb::<N, D>::block(&db, block_being_scanned) {
+          if id != block_id {
+            panic!("reorg'd from finalized {} to {}", hex::encode(id), hex::encode(block_id));
+          }
+        } else {
+          // TODO: Move this to an unwrap
+          if let Some(id) = ScannerDb::<N, D>::block(&db, block_being_scanned.saturating_sub(1)) {
+            if id != block.parent() {
+              panic!(
+                "block {} doesn't build off expected parent {}",
+                hex::encode(block_id),
+                hex::encode(id),
+              );
+            }
+          }
+
+          let mut txn = db.txn();
+          ScannerDb::<N, D>::save_block(&mut txn, block_being_scanned, &block_id);
+          txn.commit();
+        }
+
+        // Scan new blocks
+        // TODO: This lock acquisition may be long-lived...
+        let mut scanner_lock = scanner_hold.write().await;
+        let scanner = scanner_lock.as_mut().unwrap();
+
+        let mut has_activation = false;
+        let mut outputs = vec![];
+        let mut completion_block_numbers = vec![];
+        for (activation_number, key) in scanner.keys.clone() {
+          if activation_number > block_being_scanned {
+            continue;
+          }
+
+          if activation_number == block_being_scanned {
+            has_activation = true;
+          }
+
+          let key_vec = key.to_bytes().as_ref().to_vec();
+
+          // TODO: These lines are the ones which will cause a really long-lived lock acquisiton
+          for output in network.get_outputs(&block, key).await {
+            assert_eq!(output.key(), key);
+            outputs.push(output);
+          }
+
+          for (id, (block_number, tx)) in network
+            .get_eventuality_completions(scanner.eventualities.get_mut(&key_vec).unwrap(), &block)
+            .await
+          {
+            info!(
+              "eventuality {} resolved by {}, as found on chain",
+              hex::encode(id),
+              hex::encode(&tx.id())
+            );
+
+            completion_block_numbers.push(block_number);
+            // This must be before the mission of ScannerEvent::Block, per commentary in mod.rs
+            if !scanner.emit(ScannerEvent::Completed(key_vec.clone(), block_number, id, tx)).await {
+              return;
+            }
+          }
+        }
+
+        // Panic if we've already seen these outputs
+        for output in &outputs {
+          let id = output.id();
+          info!(
+            "block {} had output {} worth {}",
+            hex::encode(&block_id),
+            hex::encode(&id),
+            output.amount(),
+          );
+
+          // On Bitcoin, the output ID should be unique for a given chain
+          // On Monero, it's trivial to make an output sharing an ID with another
+          // We should only scan outputs with valid IDs however, which will be unique
+
+          /*
+            The safety of this code must satisfy the following conditions:
+            1) seen is not set for the first occurrence
+            2) seen is set for any future occurrence
+
+            seen is only written to after this code completes. Accordingly, it cannot be set
+            before the first occurrence UNLESSS it's set, yet the last scanned block isn't.
+            They are both written in the same database transaction, preventing this.
+
+            As for future occurrences, the RAM entry ensures they're handled properly even if
+            the database has yet to be set.
+
+            On reboot, which will clear the RAM, if seen wasn't set, neither was latest scanned
+            block. Accordingly, this will scan from some prior block, re-populating the RAM.
+
+            If seen was set, then this will be successfully read.
+
+            There's also no concern ram_outputs was pruned, yet seen wasn't set, as pruning
+            from ram_outputs will acquire a write lock (preventing this code from acquiring
+            its own write lock and running), and during its holding of the write lock, it
+            commits the transaction setting seen and the latest scanned block.
+
+            This last case isn't true. Committing seen/latest_scanned_block happens after
+            relinquishing the write lock.
+
+            TODO2: Only update ram_outputs after committing the TXN in question.
+          */
+          let seen = ScannerDb::<N, D>::seen(&db, &id);
+          let id = id.as_ref().to_vec();
+          if seen || scanner.ram_outputs.contains(&id) {
+            panic!("scanned an output multiple times");
+          }
+          scanner.ram_outputs.insert(id);
+        }
+
+        // We could remove this, if instead of doing the first block which passed
+        // requirements + CONFIRMATIONS, we simply emitted an event for every block where
+        // `number % CONFIRMATIONS == 0` (once at the final stage for the existing multisig)
+        // There's no need at this point, yet the latter may be more suitable for modeling...
+        async fn check_multisig_completed<N: Network, D: Db>(
+          db: &mut D,
+          multisig_completed: &mut mpsc::UnboundedReceiver<bool>,
+          block_number: usize,
+        ) -> bool {
+          match multisig_completed.recv().await {
+            None => {
+              info!("Scanner handler was dropped. Shutting down?");
+              false
+            }
+            Some(completed) => {
+              // Set the retirement block as block_number + CONFIRMATIONS
+              if completed {
+                let mut txn = db.txn();
+                // The retiring key is the earliest one still around
+                let retiring_key = ScannerDb::<N, D>::keys(&txn)[0].1;
+                // This value is static w.r.t. the key
+                ScannerDb::<N, D>::save_retirement_block(
+                  &mut txn,
+                  &retiring_key,
+                  block_number + N::CONFIRMATIONS,
+                );
+                txn.commit();
+              }
+              true
+            }
+          }
+        }
+
+        drop(scanner_lock);
+        // Now that we've dropped the Scanner lock, we need to handle the multisig_completed
+        // channel before we decide if this block should be fired or not
+        // (holding the Scanner risks a deadlock)
+        for block_number in completion_block_numbers {
+          if !check_multisig_completed::<N, _>(&mut db, &mut multisig_completed, block_number).await
+          {
+            return;
+          };
+        }
+
+        // Reacquire the scanner
+        let mut scanner_lock = scanner_hold.write().await;
+        let scanner = scanner_lock.as_mut().unwrap();
+
+        // Only emit an event if any of the following is true:
+        // - This is an activation block
+        // - This is a retirement block
+        // - There's outputs
+        // as only those are blocks are meaningful and warrant obtaining synchrony over
+        // TODO: Consider not obtaining synchrony over the retirement block depending on how the
+        // hand-off is implemented on the Substrate side of things
+        let is_retirement_block =
+          ScannerDb::<N, D>::retirement_block(&db, &scanner.keys[0].1) == Some(block_being_scanned);
+        let sent_block = if has_activation || is_retirement_block || (!outputs.is_empty()) {
+          // Save the outputs to disk
+          let mut txn = db.txn();
+          ScannerDb::<N, D>::save_outputs(&mut txn, &block_id, &outputs);
+          txn.commit();
+
+          // Send all outputs
+          if !scanner
+            .emit(ScannerEvent::Block { is_retirement_block, block: block_id, outputs })
+            .await
+          {
+            return;
+          }
+
+          scanner.need_ack.push_back(block_being_scanned);
+          true
+        } else {
+          false
+        };
+
+        // Remove it from memory
+        if is_retirement_block {
+          let retired = scanner.keys.remove(0).1;
+          scanner.eventualities.remove(retired.to_bytes().as_ref());
+        }
+
+        // Update ram_scanned/need_ack
+        scanner.ram_scanned = Some(block_being_scanned);
+
+        drop(scanner_lock);
+        // If we sent a Block event, once again check multisig_completed
+        if sent_block &&
+          (!check_multisig_completed::<N, _>(
+            &mut db,
+            &mut multisig_completed,
+            block_being_scanned,
+          )
+          .await)
+        {
+          return;
+        }
+      }
+    }
+  }
+}

processor/src/multisigs/scheduler.rs

@@ -6,7 +6,7 @@ use std::{
 use ciphersuite::{group::GroupEncoding, Ciphersuite};
 
 use crate::{
-  networks::{Output, Network},
+  networks::{OutputType, Output, Network},
   DbTxn, Db, Payment, Plan,
 };
 
@@ -29,8 +29,6 @@ pub struct Scheduler<N: Network> {
   // queued_plans are for outputs which we will create, yet when created, will have their amount
   // reduced by the fee it cost to be created. The Scheduler will then be told how what amount the
   // output actually has, and it'll be moved into plans
-  //
-  // TODO2: Consider edge case where branch/change isn't mined yet keys are deprecated
   queued_plans: HashMap<u64, VecDeque<Vec<Payment<N>>>>,
   plans: HashMap<u64, VecDeque<Vec<Payment<N>>>>,
 
@@ -46,6 +44,13 @@ fn scheduler_key<D: Db, G: GroupEncoding>(key: &G) -> Vec<u8> {
 }
 
 impl<N: Network> Scheduler<N> {
+  pub fn empty(&self) -> bool {
+    self.queued_plans.is_empty() &&
+      self.plans.is_empty() &&
+      self.utxos.is_empty() &&
+      self.payments.is_empty()
+  }
+
   fn read<R: Read>(key: <N::Curve as Ciphersuite>::G, reader: &mut R) -> io::Result<Self> {
     let mut read_plans = || -> io::Result<_> {
       let mut all_plans = HashMap::new();
@@ -93,7 +98,7 @@ impl<N: Network> Scheduler<N> {
     Ok(Scheduler { key, queued_plans, plans, utxos, payments })
   }
 
-  // TODO: Get rid of this
+  // TODO2: Get rid of this
   // We reserialize the entire scheduler on any mutation to save it to the DB which is horrible
   // We should have an incremental solution
   fn serialize(&self) -> Vec<u8> {
@@ -152,19 +157,16 @@ impl<N: Network> Scheduler<N> {
     Self::read(key, reader)
   }
 
-  fn execute(&mut self, inputs: Vec<N::Output>, mut payments: Vec<Payment<N>>) -> Plan<N> {
+  pub fn can_use_branch(&self, amount: u64) -> bool {
-    // This must be equal to plan.key due to how networks detect they created outputs which are to
+    self.plans.contains_key(&amount)
-    // the branch address
+  }
-    let branch_address = N::branch_address(self.key);
-    // created_output will be called any time we send to a branch address
-    // If it's called, and it wasn't expecting to be called, that's almost certainly an error
-    // The only way it wouldn't be is if someone on Serai triggered a burn to a branch, which is
-    // pointless anyways
-    // If we allow such behavior, we lose the ability to detect the aforementioned class of errors
-    // Ignore these payments so we can safely assert there
-    let mut payments =
-      payments.drain(..).filter(|payment| payment.address != branch_address).collect::<Vec<_>>();
 
+  fn execute(
+    &mut self,
+    inputs: Vec<N::Output>,
+    mut payments: Vec<Payment<N>>,
+    key_for_any_change: <N::Curve as Ciphersuite>::G,
+  ) -> Plan<N> {
     let mut change = false;
     let mut max = N::MAX_OUTPUTS;
 
@@ -184,6 +186,8 @@ impl<N: Network> Scheduler<N> {
       amount
     };
 
+    let branch_address = N::branch_address(self.key);
+
     // If we have more payments than we can handle in a single TX, create plans for them
     // TODO2: This isn't perfect. For 258 outputs, and a MAX_OUTPUTS of 16, this will create:
     // 15 branches of 16 leaves
@@ -207,37 +211,44 @@ impl<N: Network> Scheduler<N> {
       payments.insert(0, Payment { address: branch_address.clone(), data: None, amount });
     }
 
-    // TODO2: Use the latest key for change
+    Plan {
-    // TODO2: Update rotation documentation
+      key: self.key,
-    Plan { key: self.key, inputs, payments, change: Some(self.key).filter(|_| change) }
+      inputs,
+      payments,
+      change: Some(N::change_address(key_for_any_change)).filter(|_| change),
+    }
   }
 
-  fn add_outputs(&mut self, mut utxos: Vec<N::Output>) -> Vec<Plan<N>> {
+  fn add_outputs(
+    &mut self,
+    mut utxos: Vec<N::Output>,
+    key_for_any_change: <N::Curve as Ciphersuite>::G,
+  ) -> Vec<Plan<N>> {
     log::info!("adding {} outputs", utxos.len());
 
     let mut txs = vec![];
 
     for utxo in utxos.drain(..) {
-      // If we can fulfill planned TXs with this output, do so
+      if utxo.kind() == OutputType::Branch {
-      // We could limit this to UTXOs where `utxo.kind() == OutputType::Branch`, yet there's no
+        let amount = utxo.amount();
-      // practical benefit in doing so
+        if let Some(plans) = self.plans.get_mut(&amount) {
-      let amount = utxo.amount();
+          // Execute the first set of payments possible with an output of this amount
-      if let Some(plans) = self.plans.get_mut(&amount) {
+          let payments = plans.pop_front().unwrap();
-        // Execute the first set of payments possible with an output of this amount
+          // They won't be equal if we dropped payments due to being dust
-        let payments = plans.pop_front().unwrap();
+          assert!(amount >= payments.iter().map(|payment| payment.amount).sum::<u64>());
-        // They won't be equal if we dropped payments due to being dust
-        assert!(amount >= payments.iter().map(|payment| payment.amount).sum::<u64>());
 
-        // If we've grabbed the last plan for this output amount, remove it from the map
+          // If we've grabbed the last plan for this output amount, remove it from the map
-        if plans.is_empty() {
+          if plans.is_empty() {
-          self.plans.remove(&amount);
+            self.plans.remove(&amount);
+          }
+
+          // Create a TX for these payments
+          txs.push(self.execute(vec![utxo], payments, key_for_any_change));
+          continue;
         }
-
-        // Create a TX for these payments
-        txs.push(self.execute(vec![utxo], payments));
-      } else {
-        self.utxos.push(utxo);
       }
+
+      self.utxos.push(utxo);
     }
 
     log::info!("{} planned TXs have had their required inputs confirmed", txs.len());
@@ -249,9 +260,28 @@ impl<N: Network> Scheduler<N> {
     &mut self,
     txn: &mut D::Transaction<'_>,
     utxos: Vec<N::Output>,
-    payments: Vec<Payment<N>>,
+    mut payments: Vec<Payment<N>>,
+    key_for_any_change: <N::Curve as Ciphersuite>::G,
+    force_spend: bool,
   ) -> Vec<Plan<N>> {
-    let mut plans = self.add_outputs(utxos);
+    // Drop payments to our own branch address
+    /*
+      created_output will be called any time we send to a branch address. If it's called, and it
+      wasn't expecting to be called, that's almost certainly an error. The only way to guarantee
+      this however is to only have us send to a branch address when creating a branch, hence the
+      dropping of pointless payments.
+
+      This is not comprehensive as a payment may still be made to another active multisig's branch
+      address, depending on timing. This is safe as the issue only occurs when a multisig sends to
+      its *own* branch address, since created_output is called on the signer's Scheduler.
+    */
+    {
+      let branch_address = N::branch_address(self.key);
+      payments =
+        payments.drain(..).filter(|payment| payment.address != branch_address).collect::<Vec<_>>();
+    }
+
+    let mut plans = self.add_outputs(utxos, key_for_any_change);
 
     log::info!("scheduling {} new payments", payments.len());
 
@@ -293,10 +323,14 @@ impl<N: Network> Scheduler<N> {
 
     for chunk in utxo_chunks.drain(..) {
       // TODO: While payments have their TXs' fees deducted from themselves, that doesn't hold here
-      // We need to charge a fee before reporting incoming UTXOs to Substrate to cover aggregation
+      // We need the documented, but not yet implemented, virtual amount scheme to solve this
-      // TXs
       log::debug!("aggregating a chunk of {} inputs", N::MAX_INPUTS);
-      plans.push(Plan { key: self.key, inputs: chunk, payments: vec![], change: Some(self.key) })
+      plans.push(Plan {
+        key: self.key,
+        inputs: chunk,
+        payments: vec![],
+        change: Some(N::change_address(key_for_any_change)),
+      })
     }
 
     // We want to use all possible UTXOs for all possible payments
@@ -326,12 +360,25 @@ impl<N: Network> Scheduler<N> {
     // Now that we have the list of payments we can successfully handle right now, create the TX
     // for them
     if !executing.is_empty() {
-      plans.push(self.execute(utxos, executing));
+      plans.push(self.execute(utxos, executing, key_for_any_change));
     } else {
       // If we don't have any payments to execute, save these UTXOs for later
       self.utxos.extend(utxos);
     }
 
+    // If we're instructed to force a spend, do so
+    // This is used when an old multisig is retiring and we want to always transfer outputs to the
+    // new one, regardless if we currently have payments
+    if force_spend && (!self.utxos.is_empty()) {
+      assert!(self.utxos.len() <= N::MAX_INPUTS);
+      plans.push(Plan {
+        key: self.key,
+        inputs: self.utxos.drain(..).collect::<Vec<_>>(),
+        payments: vec![],
+        change: Some(N::change_address(key_for_any_change)),
+      });
+    }
+
     txn.put(scheduler_key::<D, _>(&self.key), self.serialize());
 
     log::info!(
@@ -342,6 +389,14 @@ impl<N: Network> Scheduler<N> {
     plans
   }
 
+  pub fn consume_payments<D: Db>(&mut self, txn: &mut D::Transaction<'_>) -> Vec<Payment<N>> {
+    let res: Vec<_> = self.payments.drain(..).collect();
+    if !res.is_empty() {
+      txn.put(scheduler_key::<D, _>(&self.key), self.serialize());
+    }
+    res
+  }
+
   // Note a branch output as having been created, with the amount it was actually created with,
   // or not having been created due to being too small
   // This can be called whenever, so long as it's properly ordered
@@ -399,7 +454,7 @@ impl<N: Network> Scheduler<N> {
     #[allow(clippy::unwrap_or_default)]
     self.plans.entry(actual).or_insert(VecDeque::new()).push_back(payments);
 
-    // TODO: This shows how ridiculous the serialize function is
+    // TODO2: This shows how ridiculous the serialize function is
     txn.put(scheduler_key::<D, _>(&self.key), self.serialize());
   }
 }

processor/src/networks/bitcoin.rs

@@ -15,6 +15,7 @@ use tokio::time::sleep;
 use bitcoin_serai::{
   bitcoin::{
     hashes::Hash as HashTrait,
+    key::{Parity, XOnlyPublicKey},
     consensus::{Encodable, Decodable},
     script::Instruction,
     address::{NetworkChecked, Address as BAddress},
@@ -45,8 +46,9 @@ use serai_client::{
 use crate::{
   networks::{
     NetworkError, Block as BlockTrait, OutputType, Output as OutputTrait,
-    Transaction as TransactionTrait, Eventuality as EventualityTrait, EventualitiesTracker,
+    Transaction as TransactionTrait, SignableTransaction as SignableTransactionTrait,
-    PostFeeBranch, Network, drop_branches, amortize_fee,
+    Eventuality as EventualityTrait, EventualitiesTracker, PostFeeBranch, Network, drop_branches,
+    amortize_fee,
   },
   Plan,
 };
@@ -76,7 +78,7 @@ pub struct Output {
   data: Vec<u8>,
 }
 
-impl OutputTrait for Output {
+impl OutputTrait<Bitcoin> for Output {
   type Id = OutputId;
 
   fn kind(&self) -> OutputType {
@@ -97,6 +99,24 @@ impl OutputTrait for Output {
     res
   }
 
+  fn tx_id(&self) -> [u8; 32] {
+    let mut hash = *self.output.outpoint().txid.as_raw_hash().as_byte_array();
+    hash.reverse();
+    hash
+  }
+
+  fn key(&self) -> ProjectivePoint {
+    let script = &self.output.output().script_pubkey;
+    assert!(script.is_v1_p2tr());
+    let Instruction::PushBytes(key) = script.instructions_minimal().last().unwrap().unwrap() else {
+      panic!("last item in v1 Taproot script wasn't bytes")
+    };
+    let key = XOnlyPublicKey::from_slice(key.as_ref())
+      .expect("last item in v1 Taproot script wasn't x-only public key");
+    Secp256k1::read_G(&mut key.public_key(Parity::Even).serialize().as_slice()).unwrap() -
+      (ProjectivePoint::GENERATOR * self.output.offset())
+  }
+
   fn balance(&self) -> Balance {
     Balance { coin: SeraiCoin::Bitcoin, amount: Amount(self.output.value()) }
   }
@@ -196,7 +216,6 @@ impl EventualityTrait for Eventuality {
 
 #[derive(Clone, Debug)]
 pub struct SignableTransaction {
-  keys: ThresholdKeys<Secp256k1>,
   transcript: RecommendedTranscript,
   actual: BSignableTransaction,
 }
@@ -206,6 +225,11 @@ impl PartialEq for SignableTransaction {
   }
 }
 impl Eq for SignableTransaction {}
+impl SignableTransactionTrait for SignableTransaction {
+  fn fee(&self) -> u64 {
+    self.actual.fee()
+  }
+}
 
 impl BlockTrait<Bitcoin> for Block {
   type Id = [u8; 32];
@@ -221,6 +245,8 @@ impl BlockTrait<Bitcoin> for Block {
     hash
   }
 
+  // TODO: Don't use this block's time, use the network time at this block
+  // TODO: Confirm network time is monotonic, enabling its usage here
   fn time(&self) -> u64 {
     self.header.time.into()
   }
@@ -231,7 +257,7 @@ impl BlockTrait<Bitcoin> for Block {
   }
 }
 
-const KEY_DST: &[u8] = b"Bitcoin Key";
+const KEY_DST: &[u8] = b"Serai Bitcoin Output Offset";
 lazy_static::lazy_static! {
   static ref BRANCH_OFFSET: Scalar = Secp256k1::hash_to_F(KEY_DST, b"branch");
   static ref CHANGE_OFFSET: Scalar = Secp256k1::hash_to_F(KEY_DST, b"change");
@@ -313,6 +339,7 @@ impl Network for Bitcoin {
 
   const NETWORK: NetworkId = NetworkId::Bitcoin;
   const ID: &'static str = "Bitcoin";
+  const ESTIMATED_BLOCK_TIME_IN_SECONDS: usize = 600;
   const CONFIRMATIONS: usize = 6;
 
   // 0.0001 BTC, 10,000 satoshis
@@ -348,6 +375,11 @@ impl Network for Bitcoin {
     Self::address(key + (ProjectivePoint::GENERATOR * offsets[&OutputType::Branch]))
   }
 
+  fn change_address(key: ProjectivePoint) -> Self::Address {
+    let (_, offsets, _) = scanner(key);
+    Self::address(key + (ProjectivePoint::GENERATOR * offsets[&OutputType::Change]))
+  }
+
   async fn get_latest_block_number(&self) -> Result<usize, NetworkError> {
     self.rpc.get_latest_block_number().await.map_err(|_| NetworkError::ConnectionError)
   }
@@ -358,11 +390,7 @@ impl Network for Bitcoin {
     self.rpc.get_block(&block_hash).await.map_err(|_| NetworkError::ConnectionError)
   }
 
-  async fn get_outputs(
+  async fn get_outputs(&self, block: &Self::Block, key: ProjectivePoint) -> Vec<Self::Output> {
-    &self,
-    block: &Self::Block,
-    key: ProjectivePoint,
-  ) -> Result<Vec<Self::Output>, NetworkError> {
     let (scanner, _, kinds) = scanner(key);
 
     let mut outputs = vec![];
@@ -390,18 +418,20 @@ impl Network for Bitcoin {
         };
         data.truncate(MAX_DATA_LEN.try_into().unwrap());
 
-        outputs.push(Output { kind, output, data })
+        let output = Output { kind, output, data };
+        assert_eq!(output.tx_id(), tx.id());
+        outputs.push(output);
       }
     }
 
-    Ok(outputs)
+    outputs
   }
 
   async fn get_eventuality_completions(
     &self,
     eventualities: &mut EventualitiesTracker<Eventuality>,
     block: &Self::Block,
-  ) -> HashMap<[u8; 32], [u8; 32]> {
+  ) -> HashMap<[u8; 32], (usize, Transaction)> {
     let mut res = HashMap::new();
     if eventualities.map.is_empty() {
       return res;
@@ -410,7 +440,7 @@ impl Network for Bitcoin {
     async fn check_block(
       eventualities: &mut EventualitiesTracker<Eventuality>,
       block: &Block,
-      res: &mut HashMap<[u8; 32], [u8; 32]>,
+      res: &mut HashMap<[u8; 32], (usize, Transaction)>,
     ) {
       for tx in &block.txdata[1 ..] {
         let input = &tx.input[0].previous_output;
@@ -430,7 +460,7 @@ impl Network for Bitcoin {
             "dishonest multisig spent input on distinct set of outputs"
           );
 
-          res.insert(plan, tx.id());
+          res.insert(plan, (eventualities.block_number, tx.clone()));
         }
       }
 
@@ -476,7 +506,6 @@ impl Network for Bitcoin {
 
   async fn prepare_send(
     &self,
-    keys: ThresholdKeys<Secp256k1>,
     _: usize,
     mut plan: Plan<Self>,
     fee: Fee,
@@ -497,10 +526,7 @@ impl Network for Bitcoin {
       match BSignableTransaction::new(
         plan.inputs.iter().map(|input| input.output.clone()).collect(),
         &payments,
-        plan.change.map(|key| {
+        plan.change.as_ref().map(|change| change.0.clone()),
-          let (_, offsets, _) = scanner(key);
-          Self::address(key + (ProjectivePoint::GENERATOR * offsets[&OutputType::Change])).0
-        }),
         None,
         fee.0,
       ) {
@@ -544,7 +570,7 @@ impl Network for Bitcoin {
 
     Ok((
       Some((
-        SignableTransaction { keys, transcript: plan.transcript(), actual: signable },
+        SignableTransaction { transcript: plan.transcript(), actual: signable },
         Eventuality { plan_binding_input, outputs },
       )),
       branch_outputs,
@@ -553,13 +579,14 @@ impl Network for Bitcoin {
 
   async fn attempt_send(
     &self,
+    keys: ThresholdKeys<Self::Curve>,
     transaction: Self::SignableTransaction,
   ) -> Result<Self::TransactionMachine, NetworkError> {
     Ok(
       transaction
         .actual
         .clone()
-        .multisig(transaction.keys.clone(), transaction.transcript)
+        .multisig(keys.clone(), transaction.transcript)
         .expect("used the wrong keys"),
     )
   }

processor/src/networks/mod.rs

@@ -1,4 +1,4 @@
-use core::fmt::Debug;
+use core::{fmt::Debug, time::Duration};
 use std::{io, collections::HashMap};
 
 use async_trait::async_trait;
@@ -12,6 +12,10 @@ use frost::{
 
 use serai_client::primitives::{NetworkId, Balance};
 
+use log::error;
+
+use tokio::time::sleep;
+
 #[cfg(feature = "bitcoin")]
 pub mod bitcoin;
 #[cfg(feature = "bitcoin")]
@@ -90,14 +94,17 @@ impl OutputType {
   }
 }
 
-pub trait Output: Send + Sync + Sized + Clone + PartialEq + Eq + Debug {
+pub trait Output<N: Network>: Send + Sync + Sized + Clone + PartialEq + Eq + Debug {
   type Id: 'static + Id;
 
   fn kind(&self) -> OutputType;
 
   fn id(&self) -> Self::Id;
+  fn tx_id(&self) -> <N::Transaction as Transaction<N>>::Id;
+  fn key(&self) -> <N::Curve as Ciphersuite>::G;
 
   fn balance(&self) -> Balance;
+  // TODO: Remove this?
   fn amount(&self) -> u64 {
     self.balance().amount.0
   }
@@ -117,6 +124,10 @@ pub trait Transaction<N: Network>: Send + Sync + Sized + Clone + Debug {
   async fn fee(&self, network: &N) -> u64;
 }
 
+pub trait SignableTransaction: Send + Sync + Clone + Debug {
+  fn fee(&self) -> u64;
+}
+
 pub trait Eventuality: Send + Sync + Clone + Debug {
   fn lookup(&self) -> Vec<u8>;
 
@@ -172,10 +183,11 @@ impl<E: Eventuality> Default for EventualitiesTracker<E> {
 }
 
 pub trait Block<N: Network>: Send + Sync + Sized + Clone + Debug {
-  // This is currently bounded to being 32-bytes.
+  // This is currently bounded to being 32 bytes.
   type Id: 'static + Id;
   fn id(&self) -> Self::Id;
   fn parent(&self) -> Self::Id;
+  // The monotonic network time at this block.
   fn time(&self) -> u64;
   fn median_fee(&self) -> N::Fee;
 }
@@ -275,9 +287,9 @@ pub trait Network: 'static + Send + Sync + Clone + PartialEq + Eq + Debug {
 
   /// The type containing all information on a scanned output.
   // This is almost certainly distinct from the network's native output type.
-  type Output: Output;
+  type Output: Output<Self>;
   /// The type containing all information on a planned transaction, waiting to be signed.
-  type SignableTransaction: Send + Sync + Clone + Debug;
+  type SignableTransaction: SignableTransaction;
   /// The type containing all information to check if a plan was completed.
   ///
   /// This must be binding to both the outputs expected and the plan ID.
@@ -302,6 +314,8 @@ pub trait Network: 'static + Send + Sync + Clone + PartialEq + Eq + Debug {
   const NETWORK: NetworkId;
   /// String ID for this network.
   const ID: &'static str;
+  /// The estimated amount of time a block will take.
+  const ESTIMATED_BLOCK_TIME_IN_SECONDS: usize;
   /// The amount of confirmations required to consider a block 'final'.
   const CONFIRMATIONS: usize;
   /// The maximum amount of inputs which will fit in a TX.
@@ -322,8 +336,9 @@ pub trait Network: 'static + Send + Sync + Clone + PartialEq + Eq + Debug {
   /// Address for the given group key to receive external coins to.
   fn address(key: <Self::Curve as Ciphersuite>::G) -> Self::Address;
   /// Address for the given group key to use for scheduled branches.
-  // This is purely used for debugging purposes. Any output may be used to execute a branch.
   fn branch_address(key: <Self::Curve as Ciphersuite>::G) -> Self::Address;
+  /// Address for the given group key to use for change.
+  fn change_address(key: <Self::Curve as Ciphersuite>::G) -> Self::Address;
 
   /// Get the latest block's number.
   async fn get_latest_block_number(&self) -> Result<usize, NetworkError>;
@@ -334,24 +349,26 @@ pub trait Network: 'static + Send + Sync + Clone + PartialEq + Eq + Debug {
     &self,
     block: &Self::Block,
     key: <Self::Curve as Ciphersuite>::G,
-  ) -> Result<Vec<Self::Output>, NetworkError>;
+  ) -> Vec<Self::Output>;
 
   /// Get the registered eventualities completed within this block, and any prior blocks which
   /// registered eventualities may have been completed in.
   ///
-  /// This will panic if not fed a new block.
+  /// This may panic if not fed a block greater than the tracker's block number.
+  // TODO: get_eventuality_completions_internal + provided get_eventuality_completions for common
+  // code
   async fn get_eventuality_completions(
     &self,
     eventualities: &mut EventualitiesTracker<Self::Eventuality>,
     block: &Self::Block,
-  ) -> HashMap<[u8; 32], <Self::Transaction as Transaction<Self>>::Id>;
+  ) -> HashMap<[u8; 32], (usize, Self::Transaction)>;
 
   /// Prepare a SignableTransaction for a transaction.
+  ///
   /// Returns None for the transaction if the SignableTransaction was dropped due to lack of value.
   #[rustfmt::skip]
   async fn prepare_send(
     &self,
-    keys: ThresholdKeys<Self::Curve>,
     block_number: usize,
     plan: Plan<Self>,
     fee: Self::Fee,
@@ -363,6 +380,7 @@ pub trait Network: 'static + Send + Sync + Clone + PartialEq + Eq + Debug {
   /// Attempt to sign a SignableTransaction.
   async fn attempt_send(
     &self,
+    keys: ThresholdKeys<Self::Curve>,
     transaction: Self::SignableTransaction,
   ) -> Result<Self::TransactionMachine, NetworkError>;
 
@@ -396,3 +414,35 @@ pub trait Network: 'static + Send + Sync + Clone + PartialEq + Eq + Debug {
   #[cfg(test)]
   async fn test_send(&self, key: Self::Address) -> Self::Block;
 }
+
+// TODO: Move into above trait
+pub async fn get_latest_block_number<N: Network>(network: &N) -> usize {
+  loop {
+    match network.get_latest_block_number().await {
+      Ok(number) => {
+        return number;
+      }
+      Err(e) => {
+        error!(
+          "couldn't get the latest block number in main's error-free get_block. {} {}",
+          "this should only happen if the node is offline. error: ", e
+        );
+        sleep(Duration::from_secs(10)).await;
+      }
+    }
+  }
+}
+
+pub async fn get_block<N: Network>(network: &N, block_number: usize) -> N::Block {
+  loop {
+    match network.get_block(block_number).await {
+      Ok(block) => {
+        return block;
+      }
+      Err(e) => {
+        error!("couldn't get block {block_number} in main's error-free get_block. error: {}", e);
+        sleep(Duration::from_secs(10)).await;
+      }
+    }
+  }
+}

processor/src/networks/monero.rs

@@ -37,8 +37,9 @@ use crate::{
   Payment, Plan, additional_key,
   networks::{
     NetworkError, Block as BlockTrait, OutputType, Output as OutputTrait,
-    Transaction as TransactionTrait, Eventuality as EventualityTrait, EventualitiesTracker,
+    Transaction as TransactionTrait, SignableTransaction as SignableTransactionTrait,
-    PostFeeBranch, Network, drop_branches, amortize_fee,
+    Eventuality as EventualityTrait, EventualitiesTracker, PostFeeBranch, Network, drop_branches,
+    amortize_fee,
   },
 };
 
@@ -49,7 +50,7 @@ const EXTERNAL_SUBADDRESS: Option<SubaddressIndex> = SubaddressIndex::new(0, 0);
 const BRANCH_SUBADDRESS: Option<SubaddressIndex> = SubaddressIndex::new(1, 0);
 const CHANGE_SUBADDRESS: Option<SubaddressIndex> = SubaddressIndex::new(2, 0);
 
-impl OutputTrait for Output {
+impl OutputTrait<Monero> for Output {
   // While we could use (tx, o), using the key ensures we won't be susceptible to the burning bug.
   // While we already are immune, thanks to using featured address, this doesn't hurt and is
   // technically more efficient.
@@ -68,6 +69,14 @@ impl OutputTrait for Output {
     self.0.output.data.key.compress().to_bytes()
   }
 
+  fn tx_id(&self) -> [u8; 32] {
+    self.0.output.absolute.tx
+  }
+
+  fn key(&self) -> EdwardsPoint {
+    EdwardsPoint(self.0.output.data.key - (EdwardsPoint::generator().0 * self.0.key_offset()))
+  }
+
   fn balance(&self) -> Balance {
     Balance { coin: SeraiCoin::Monero, amount: Amount(self.0.commitment().amount) }
   }
@@ -130,10 +139,14 @@ impl EventualityTrait for Eventuality {
 
 #[derive(Clone, Debug)]
 pub struct SignableTransaction {
-  keys: ThresholdKeys<Ed25519>,
   transcript: RecommendedTranscript,
   actual: MSignableTransaction,
 }
+impl SignableTransactionTrait for SignableTransaction {
+  fn fee(&self) -> u64 {
+    self.actual.fee()
+  }
+}
 
 impl BlockTrait<Monero> for Block {
   type Id = [u8; 32];
@@ -145,6 +158,7 @@ impl BlockTrait<Monero> for Block {
     self.header.previous
   }
 
+  // TODO: Check Monero enforces this to be monotonic and sane
   fn time(&self) -> u64 {
     self.header.timestamp
   }
@@ -227,6 +241,7 @@ impl Network for Monero {
 
   const NETWORK: NetworkId = NetworkId::Monero;
   const ID: &'static str = "Monero";
+  const ESTIMATED_BLOCK_TIME_IN_SECONDS: usize = 120;
   const CONFIRMATIONS: usize = 10;
 
   // wallet2 will not create a transaction larger than 100kb, and Monero won't relay a transaction
@@ -250,6 +265,10 @@ impl Network for Monero {
     Self::address_internal(key, BRANCH_SUBADDRESS)
   }
 
+  fn change_address(key: EdwardsPoint) -> Self::Address {
+    Self::address_internal(key, CHANGE_SUBADDRESS)
+  }
+
   async fn get_latest_block_number(&self) -> Result<usize, NetworkError> {
     // Monero defines height as chain length, so subtract 1 for block number
     Ok(self.rpc.get_height().await.map_err(|_| NetworkError::ConnectionError)? - 1)
@@ -267,15 +286,19 @@ impl Network for Monero {
     )
   }
 
-  async fn get_outputs(
+  async fn get_outputs(&self, block: &Block, key: EdwardsPoint) -> Vec<Self::Output> {
-    &self,
+    let outputs = loop {
-    block: &Block,
+      match Self::scanner(key).scan(&self.rpc, block).await {
-    key: EdwardsPoint,
+        Ok(outputs) => break outputs,
-  ) -> Result<Vec<Self::Output>, NetworkError> {
+        Err(e) => {
-    let mut txs = Self::scanner(key)
+          log::error!("couldn't scan block {}: {e:?}", hex::encode(block.id()));
-      .scan(&self.rpc, block)
+          sleep(Duration::from_secs(60)).await;
-      .await
+          continue;
-      .map_err(|_| NetworkError::ConnectionError)?
+        }
+      }
+    };
+
+    let mut txs = outputs
       .iter()
       .filter_map(|outputs| Some(outputs.not_locked()).filter(|outputs| !outputs.is_empty()))
       .collect::<Vec<_>>();
@@ -305,14 +328,14 @@ impl Network for Monero {
       }
     }
 
-    Ok(outputs)
+    outputs
   }
 
   async fn get_eventuality_completions(
     &self,
     eventualities: &mut EventualitiesTracker<Eventuality>,
     block: &Block,
-  ) -> HashMap<[u8; 32], [u8; 32]> {
+  ) -> HashMap<[u8; 32], (usize, Transaction)> {
     let mut res = HashMap::new();
     if eventualities.map.is_empty() {
       return res;
@@ -322,7 +345,7 @@ impl Network for Monero {
       network: &Monero,
       eventualities: &mut EventualitiesTracker<Eventuality>,
       block: &Block,
-      res: &mut HashMap<[u8; 32], [u8; 32]>,
+      res: &mut HashMap<[u8; 32], (usize, Transaction)>,
     ) {
       for hash in &block.txs {
         let tx = {
@@ -339,7 +362,7 @@ impl Network for Monero {
 
         if let Some((_, eventuality)) = eventualities.map.get(&tx.prefix.extra) {
           if eventuality.matches(&tx) {
-            res.insert(eventualities.map.remove(&tx.prefix.extra).unwrap().0, tx.hash());
+            res.insert(eventualities.map.remove(&tx.prefix.extra).unwrap().0, (block.number(), tx));
           }
         }
       }
@@ -373,7 +396,6 @@ impl Network for Monero {
 
   async fn prepare_send(
     &self,
-    keys: ThresholdKeys<Ed25519>,
     block_number: usize,
     mut plan: Plan<Self>,
     fee: Fee,
@@ -457,9 +479,7 @@ impl Network for Monero {
         Some(Zeroizing::new(plan.id())),
         inputs.clone(),
         payments,
-        plan.change.map(|key| {
+        plan.change.map(|change| Change::fingerprintable(change.into())),
-          Change::fingerprintable(Self::address_internal(key, CHANGE_SUBADDRESS).into())
-        }),
         vec![],
         fee,
       ) {
@@ -509,7 +529,6 @@ impl Network for Monero {
     let branch_outputs = amortize_fee(&mut plan, tx_fee);
 
     let signable = SignableTransaction {
-      keys,
       transcript,
       actual: match signable(plan, Some(tx_fee))? {
         Some(signable) => signable,
@@ -522,9 +541,10 @@ impl Network for Monero {
 
   async fn attempt_send(
     &self,
+    keys: ThresholdKeys<Self::Curve>,
     transaction: SignableTransaction,
   ) -> Result<Self::TransactionMachine, NetworkError> {
-    match transaction.actual.clone().multisig(transaction.keys.clone(), transaction.transcript) {
+    match transaction.actual.clone().multisig(keys, transaction.transcript) {
       Ok(machine) => Ok(machine),
       Err(e) => panic!("failed to create a multisig machine for TX: {e}"),
     }

processor/src/plan.rs

@@ -24,6 +24,7 @@ impl<N: Network> Payment<N> {
   }
 
   pub fn write<W: io::Write>(&self, writer: &mut W) -> io::Result<()> {
+    // TODO: Don't allow creating Payments with an Address which can't be serialized
     let address: Vec<u8> = self
       .address
       .clone()
@@ -74,7 +75,7 @@ pub struct Plan<N: Network> {
   pub key: <N::Curve as Ciphersuite>::G,
   pub inputs: Vec<N::Output>,
   pub payments: Vec<Payment<N>>,
-  pub change: Option<<N::Curve as Ciphersuite>::G>,
+  pub change: Option<N::Address>,
 }
 impl<N: Network> core::fmt::Debug for Plan<N> {
   fn fmt(&self, fmt: &mut core::fmt::Formatter<'_>) -> Result<(), core::fmt::Error> {
@@ -83,7 +84,7 @@ impl<N: Network> core::fmt::Debug for Plan<N> {
       .field("key", &hex::encode(self.key.to_bytes()))
       .field("inputs", &self.inputs)
       .field("payments", &self.payments)
-      .field("change", &self.change.map(|change| hex::encode(change.to_bytes())))
+      .field("change", &self.change.as_ref().map(|change| change.to_string()))
       .finish()
   }
 }
@@ -105,8 +106,8 @@ impl<N: Network> Plan<N> {
       payment.transcript(&mut transcript);
     }
 
-    if let Some(change) = self.change {
+    if let Some(change) = &self.change {
-      transcript.append_message(b"change", change.to_bytes());
+      transcript.append_message(b"change", change.to_string());
     }
 
     transcript
@@ -132,12 +133,23 @@ impl<N: Network> Plan<N> {
       payment.write(writer)?;
     }
 
-    writer.write_all(&[u8::from(self.change.is_some())])?;
+    // TODO: Have Plan construction fail if change cannot be serialized
-    if let Some(change) = &self.change {
+    let change = if let Some(change) = &self.change {
-      writer.write_all(change.to_bytes().as_ref())?;
+      change.clone().try_into().map_err(|_| {
-    }
+        io::Error::new(
-
+          io::ErrorKind::Other,
-    Ok(())
+          format!(
+            "an address we said to use as change couldn't be convered to a Vec<u8>: {}",
+            change.to_string(),
+          ),
+        )
+      })?
+    } else {
+      vec![]
+    };
+    assert!(serai_client::primitives::MAX_ADDRESS_LEN <= u8::MAX.into());
+    writer.write_all(&[u8::try_from(change.len()).unwrap()])?;
+    writer.write_all(&change)
   }
 
   pub fn read<R: io::Read>(reader: &mut R) -> io::Result<Self> {
@@ -156,9 +168,20 @@ impl<N: Network> Plan<N> {
       payments.push(Payment::<N>::read(reader)?);
     }
 
-    let mut buf = [0; 1];
+    let mut len = [0; 1];
-    reader.read_exact(&mut buf)?;
+    reader.read_exact(&mut len)?;
-    let change = if buf[0] == 1 { Some(N::Curve::read_G(reader)?) } else { None };
+    let mut change = vec![0; usize::from(len[0])];
+    reader.read_exact(&mut change)?;
+    let change = if change.is_empty() {
+      None
+    } else {
+      Some(N::Address::try_from(change).map_err(|_| {
+        io::Error::new(
+          io::ErrorKind::Other,
+          "couldn't deserialize an Address serialized into a Plan",
+        )
+      })?)
+    };
 
     Ok(Plan { key, inputs, payments, change })
   }

processor/src/scanner.rs

@@ -1,525 +0,0 @@
-use core::marker::PhantomData;
-use std::{
-  sync::Arc,
-  time::Duration,
-  collections::{HashSet, HashMap},
-};
-
-use ciphersuite::group::GroupEncoding;
-use frost::curve::Ciphersuite;
-
-use log::{info, debug, warn};
-use tokio::{
-  sync::{RwLock, mpsc},
-  time::sleep,
-};
-
-use crate::{
-  Get, DbTxn, Db,
-  networks::{Output, Transaction, EventualitiesTracker, Block, Network},
-};
-
-#[derive(Clone, Debug)]
-pub enum ScannerEvent<N: Network> {
-  // Block scanned
-  Block { block: <N::Block as Block<N>>::Id, outputs: Vec<N::Output> },
-  // Eventuality completion found on-chain
-  Completed([u8; 32], <N::Transaction as Transaction<N>>::Id),
-}
-
-pub type ScannerEventChannel<N> = mpsc::UnboundedReceiver<ScannerEvent<N>>;
-
-#[derive(Clone, Debug)]
-struct ScannerDb<N: Network, D: Db>(PhantomData<N>, PhantomData<D>);
-impl<N: Network, D: Db> ScannerDb<N, D> {
-  fn scanner_key(dst: &'static [u8], key: impl AsRef<[u8]>) -> Vec<u8> {
-    D::key(b"SCANNER", dst, key)
-  }
-
-  fn block_key(number: usize) -> Vec<u8> {
-    Self::scanner_key(b"block_id", u64::try_from(number).unwrap().to_le_bytes())
-  }
-  fn block_number_key(id: &<N::Block as Block<N>>::Id) -> Vec<u8> {
-    Self::scanner_key(b"block_number", id)
-  }
-  fn save_block(txn: &mut D::Transaction<'_>, number: usize, id: &<N::Block as Block<N>>::Id) {
-    txn.put(Self::block_number_key(id), u64::try_from(number).unwrap().to_le_bytes());
-    txn.put(Self::block_key(number), id);
-  }
-  fn block<G: Get>(getter: &G, number: usize) -> Option<<N::Block as Block<N>>::Id> {
-    getter.get(Self::block_key(number)).map(|id| {
-      let mut res = <N::Block as Block<N>>::Id::default();
-      res.as_mut().copy_from_slice(&id);
-      res
-    })
-  }
-  fn block_number<G: Get>(getter: &G, id: &<N::Block as Block<N>>::Id) -> Option<usize> {
-    getter
-      .get(Self::block_number_key(id))
-      .map(|number| u64::from_le_bytes(number.try_into().unwrap()).try_into().unwrap())
-  }
-
-  fn active_keys_key() -> Vec<u8> {
-    Self::scanner_key(b"active_keys", b"")
-  }
-  fn add_active_key(txn: &mut D::Transaction<'_>, key: <N::Curve as Ciphersuite>::G) {
-    let mut keys = txn.get(Self::active_keys_key()).unwrap_or(vec![]);
-
-    let key_bytes = key.to_bytes();
-
-    let key_len = key_bytes.as_ref().len();
-    assert_eq!(keys.len() % key_len, 0);
-
-    // Don't add this key if it's already present
-    let mut i = 0;
-    while i < keys.len() {
-      if &keys[i .. (i + key_len)] == key_bytes.as_ref() {
-        debug!("adding {} as an active key yet it was already present", hex::encode(key_bytes));
-        return;
-      }
-      i += key_len;
-    }
-
-    keys.extend(key_bytes.as_ref());
-    txn.put(Self::active_keys_key(), keys);
-  }
-  fn active_keys<G: Get>(getter: &G) -> Vec<<N::Curve as Ciphersuite>::G> {
-    let bytes_vec = getter.get(Self::active_keys_key()).unwrap_or(vec![]);
-    let mut bytes: &[u8] = bytes_vec.as_ref();
-
-    // Assumes keys will be 32 bytes when calculating the capacity
-    // If keys are larger, this may allocate more memory than needed
-    // If keys are smaller, this may require additional allocations
-    // Either are fine
-    let mut res = Vec::with_capacity(bytes.len() / 32);
-    while !bytes.is_empty() {
-      res.push(N::Curve::read_G(&mut bytes).unwrap());
-    }
-    res
-  }
-
-  fn seen_key(id: &<N::Output as Output>::Id) -> Vec<u8> {
-    Self::scanner_key(b"seen", id)
-  }
-  fn seen<G: Get>(getter: &G, id: &<N::Output as Output>::Id) -> bool {
-    getter.get(Self::seen_key(id)).is_some()
-  }
-
-  fn next_batch_key() -> Vec<u8> {
-    Self::scanner_key(b"next_batch", [])
-  }
-  fn outputs_key(
-    key: &<N::Curve as Ciphersuite>::G,
-    block: &<N::Block as Block<N>>::Id,
-  ) -> Vec<u8> {
-    Self::scanner_key(b"outputs", [key.to_bytes().as_ref(), block.as_ref()].concat())
-  }
-  fn save_outputs(
-    txn: &mut D::Transaction<'_>,
-    key: &<N::Curve as Ciphersuite>::G,
-    block: &<N::Block as Block<N>>::Id,
-    outputs: &[N::Output],
-  ) {
-    let mut bytes = Vec::with_capacity(outputs.len() * 64);
-    for output in outputs {
-      output.write(&mut bytes).unwrap();
-    }
-    txn.put(Self::outputs_key(key, block), bytes);
-
-    // This is a new set of outputs, which are expected to be handled in a perfectly ordered
-    // fashion
-
-    // TODO2: This is not currently how this works
-    // There may be new blocks 0 .. 5, which A will scan, yet then B may be activated at block 4
-    // This would cause
-    // 0a, 1a, 2a, 3a, 4a, 5a, 4b, 5b
-    // when it should be
-    // 0a, 1a, 2a, 3a, 4a, 4b, 5a, 5b
-  }
-  fn outputs(
-    txn: &D::Transaction<'_>,
-    key: &<N::Curve as Ciphersuite>::G,
-    block: &<N::Block as Block<N>>::Id,
-  ) -> Option<Vec<N::Output>> {
-    let bytes_vec = txn.get(Self::outputs_key(key, block))?;
-    let mut bytes: &[u8] = bytes_vec.as_ref();
-
-    let mut res = vec![];
-    while !bytes.is_empty() {
-      res.push(N::Output::read(&mut bytes).unwrap());
-    }
-    Some(res)
-  }
-
-  fn scanned_block_key(key: &<N::Curve as Ciphersuite>::G) -> Vec<u8> {
-    Self::scanner_key(b"scanned_block", key.to_bytes())
-  }
-
-  #[allow(clippy::type_complexity)]
-  fn save_scanned_block(
-    txn: &mut D::Transaction<'_>,
-    key: &<N::Curve as Ciphersuite>::G,
-    block: usize,
-  ) -> Vec<N::Output> {
-    let id = Self::block(txn, block); // It may be None for the first key rotated to
-    let outputs = if let Some(id) = id.as_ref() {
-      Self::outputs(txn, key, id).unwrap_or(vec![])
-    } else {
-      vec![]
-    };
-
-    // Mark all the outputs from this block as seen
-    for output in &outputs {
-      txn.put(Self::seen_key(&output.id()), b"");
-    }
-
-    txn.put(Self::scanned_block_key(key), u64::try_from(block).unwrap().to_le_bytes());
-
-    // Return this block's outputs so they can be pruned from the RAM cache
-    outputs
-  }
-  fn latest_scanned_block<G: Get>(getter: &G, key: <N::Curve as Ciphersuite>::G) -> usize {
-    let bytes = getter
-      .get(Self::scanned_block_key(&key))
-      .expect("asking for latest scanned block of key which wasn't rotated to");
-    u64::from_le_bytes(bytes.try_into().unwrap()).try_into().unwrap()
-  }
-}
-
-/// The Scanner emits events relating to the blockchain, notably received outputs.
-/// It WILL NOT fail to emit an event, even if it reboots at selected moments.
-/// It MAY fire the same event multiple times.
-#[derive(Debug)]
-pub struct Scanner<N: Network, D: Db> {
-  network: N,
-  db: D,
-  keys: Vec<<N::Curve as Ciphersuite>::G>,
-
-  eventualities: EventualitiesTracker<N::Eventuality>,
-
-  ram_scanned: HashMap<Vec<u8>, usize>,
-  ram_outputs: HashSet<Vec<u8>>,
-
-  events: mpsc::UnboundedSender<ScannerEvent<N>>,
-}
-
-#[derive(Debug)]
-pub struct ScannerHandle<N: Network, D: Db> {
-  scanner: Arc<RwLock<Scanner<N, D>>>,
-  pub events: ScannerEventChannel<N>,
-}
-
-impl<N: Network, D: Db> ScannerHandle<N, D> {
-  pub async fn ram_scanned(&self) -> usize {
-    let mut res = None;
-    for scanned in self.scanner.read().await.ram_scanned.values() {
-      if res.is_none() {
-        res = Some(*scanned);
-      }
-      // Returns the lowest scanned value so no matter the keys interacted with, this is
-      // sufficiently scanned
-      res = Some(res.unwrap().min(*scanned));
-    }
-    res.unwrap_or(0)
-  }
-
-  pub async fn register_eventuality(
-    &mut self,
-    block_number: usize,
-    id: [u8; 32],
-    eventuality: N::Eventuality,
-  ) {
-    self.scanner.write().await.eventualities.register(block_number, id, eventuality)
-  }
-
-  pub async fn drop_eventuality(&mut self, id: [u8; 32]) {
-    self.scanner.write().await.eventualities.drop(id);
-  }
-
-  /// Rotate the key being scanned for.
-  ///
-  /// If no key has been prior set, this will become the key with no further actions.
-  ///
-  /// If a key has been prior set, both keys will be scanned for as detailed in the Multisig
-  /// documentation. The old key will eventually stop being scanned for, leaving just the
-  /// updated-to key.
-  pub async fn rotate_key(
-    &mut self,
-    txn: &mut D::Transaction<'_>,
-    activation_number: usize,
-    key: <N::Curve as Ciphersuite>::G,
-  ) {
-    let mut scanner = self.scanner.write().await;
-    if !scanner.keys.is_empty() {
-      // Protonet will have a single, static validator set
-      // TODO2
-      panic!("only a single key is supported at this time");
-    }
-
-    info!("Rotating scanner to key {} at {activation_number}", hex::encode(key.to_bytes()));
-
-    let outputs = ScannerDb::<N, D>::save_scanned_block(txn, &key, activation_number);
-    scanner.ram_scanned.insert(key.to_bytes().as_ref().to_vec(), activation_number);
-    assert!(outputs.is_empty());
-
-    ScannerDb::<N, D>::add_active_key(txn, key);
-    scanner.keys.push(key);
-  }
-
-  // This perform a database read which isn't safe with regards to if the value is set or not
-  // It may be set, when it isn't expected to be set, or not set, when it is expected to be set
-  // Since the value is static, if it's set, it's correctly set
-  pub async fn block_number(&self, id: &<N::Block as Block<N>>::Id) -> Option<usize> {
-    ScannerDb::<N, D>::block_number(&self.scanner.read().await.db, id)
-  }
-
-  // Set the next batch ID to use
-  pub fn set_next_batch_id(&self, txn: &mut D::Transaction<'_>, batch: u32) {
-    txn.put(ScannerDb::<N, D>::next_batch_key(), batch.to_le_bytes());
-  }
-
-  // Get the next batch ID
-  pub fn next_batch_id(&self, txn: &D::Transaction<'_>) -> u32 {
-    txn
-      .get(ScannerDb::<N, D>::next_batch_key())
-      .map_or(0, |v| u32::from_le_bytes(v.try_into().unwrap()))
-  }
-
-  /// Acknowledge having handled a block for a key.
-  pub async fn ack_up_to_block(
-    &mut self,
-    txn: &mut D::Transaction<'_>,
-    key: <N::Curve as Ciphersuite>::G,
-    id: <N::Block as Block<N>>::Id,
-  ) -> Vec<N::Output> {
-    let mut scanner = self.scanner.write().await;
-    debug!("Block {} acknowledged", hex::encode(&id));
-
-    // Get the number for this block
-    let number = ScannerDb::<N, D>::block_number(txn, &id)
-      .expect("main loop trying to operate on data we haven't scanned");
-    // Get the number of the last block we acknowledged
-    let prior = ScannerDb::<N, D>::latest_scanned_block(txn, key);
-
-    let mut outputs = vec![];
-    for number in (prior + 1) ..= number {
-      outputs.extend(ScannerDb::<N, D>::save_scanned_block(txn, &key, number));
-    }
-
-    for output in &outputs {
-      assert!(scanner.ram_outputs.remove(output.id().as_ref()));
-    }
-
-    outputs
-  }
-}
-
-impl<N: Network, D: Db> Scanner<N, D> {
-  #[allow(clippy::new_ret_no_self)]
-  pub fn new(network: N, db: D) -> (ScannerHandle<N, D>, Vec<<N::Curve as Ciphersuite>::G>) {
-    let (events_send, events_recv) = mpsc::unbounded_channel();
-
-    let keys = ScannerDb::<N, D>::active_keys(&db);
-    let mut ram_scanned = HashMap::new();
-    for key in keys.clone() {
-      ram_scanned.insert(
-        key.to_bytes().as_ref().to_vec(),
-        ScannerDb::<N, D>::latest_scanned_block(&db, key),
-      );
-    }
-
-    let scanner = Arc::new(RwLock::new(Scanner {
-      network,
-      db,
-      keys: keys.clone(),
-
-      eventualities: EventualitiesTracker::new(),
-
-      ram_scanned,
-      ram_outputs: HashSet::new(),
-
-      events: events_send,
-    }));
-    tokio::spawn(Scanner::run(scanner.clone()));
-
-    (ScannerHandle { scanner, events: events_recv }, keys)
-  }
-
-  fn emit(&mut self, event: ScannerEvent<N>) -> bool {
-    if self.events.send(event).is_err() {
-      info!("Scanner handler was dropped. Shutting down?");
-      return false;
-    }
-    true
-  }
-
-  // An async function, to be spawned on a task, to discover and report outputs
-  async fn run(scanner: Arc<RwLock<Self>>) {
-    loop {
-      // Only check every five seconds for new blocks
-      sleep(Duration::from_secs(5)).await;
-
-      // Scan new blocks
-      {
-        let mut scanner = scanner.write().await;
-        let latest = scanner.network.get_latest_block_number().await;
-        let latest = match latest {
-          // Only scan confirmed blocks, which we consider effectively finalized
-          // CONFIRMATIONS - 1 as whatever's in the latest block already has 1 confirm
-          Ok(latest) => latest.saturating_sub(N::CONFIRMATIONS.saturating_sub(1)),
-          Err(_) => {
-            warn!("couldn't get latest block number");
-            sleep(Duration::from_secs(60)).await;
-            continue;
-          }
-        };
-
-        for key in scanner.keys.clone() {
-          let key_vec = key.to_bytes().as_ref().to_vec();
-          let latest_scanned = scanner.ram_scanned[&key_vec];
-
-          for i in (latest_scanned + 1) ..= latest {
-            // TODO2: Check for key deprecation
-
-            let block = match scanner.network.get_block(i).await {
-              Ok(block) => block,
-              Err(_) => {
-                warn!("couldn't get block {i}");
-                break;
-              }
-            };
-            let block_id = block.id();
-
-            // These block calls are safe, despite not having a txn, since they're static values
-            // only written to/read by this thread
-            // There's also no error caused by them being unexpectedly written (if the commit is
-            // made and then the processor suddenly reboots)
-            // There's also no issue if this code is run multiple times (due to code after
-            // aborting)
-            if let Some(id) = ScannerDb::<N, D>::block(&scanner.db, i) {
-              if id != block_id {
-                panic!("reorg'd from finalized {} to {}", hex::encode(id), hex::encode(block_id));
-              }
-            } else {
-              info!("Found new block: {}", hex::encode(&block_id));
-
-              if let Some(id) = ScannerDb::<N, D>::block(&scanner.db, i.saturating_sub(1)) {
-                if id != block.parent() {
-                  panic!(
-                    "block {} doesn't build off expected parent {}",
-                    hex::encode(block_id),
-                    hex::encode(id),
-                  );
-                }
-              }
-
-              let mut txn = scanner.db.txn();
-              ScannerDb::<N, D>::save_block(&mut txn, i, &block_id);
-              txn.commit();
-            }
-
-            let outputs = match scanner.network.get_outputs(&block, key).await {
-              Ok(outputs) => outputs,
-              Err(_) => {
-                warn!("couldn't scan block {i}");
-                break;
-              }
-            };
-
-            // Write this number as scanned so we won't perform any of the following mutations
-            // multiple times
-            scanner.ram_scanned.insert(key_vec.clone(), i);
-
-            // Panic if we've already seen these outputs
-            for output in &outputs {
-              let id = output.id();
-              info!(
-                "block {} had output {} worth {}",
-                hex::encode(&block_id),
-                hex::encode(&id),
-                output.amount(),
-              );
-
-              // On Bitcoin, the output ID should be unique for a given chain
-              // On Monero, it's trivial to make an output sharing an ID with another
-              // We should only scan outputs with valid IDs however, which will be unique
-
-              /*
-                The safety of this code must satisfy the following conditions:
-                1) seen is not set for the first occurrence
-                2) seen is set for any future occurrence
-
-                seen is only written to after this code completes. Accordingly, it cannot be set
-                before the first occurrence UNLESSS it's set, yet the last scanned block isn't.
-                They are both written in the same database transaction, preventing this.
-
-                As for future occurrences, the RAM entry ensures they're handled properly even if
-                the database has yet to be set.
-
-                On reboot, which will clear the RAM, if seen wasn't set, neither was latest scanned
-                block. Accordingly, this will scan from some prior block, re-populating the RAM.
-
-                If seen was set, then this will be successfully read.
-
-                There's also no concern ram_outputs was pruned, yet seen wasn't set, as pruning
-                from ram_outputs will acquire a write lock (preventing this code from acquiring
-                its own write lock and running), and during its holding of the write lock, it
-                commits the transaction setting seen and the latest scanned block.
-
-                This last case isn't true. Committing seen/latest_scanned_block happens after
-                relinquishing the write lock.
-
-                TODO: Only update ram_outputs after committing the TXN in question.
-              */
-              let seen = ScannerDb::<N, D>::seen(&scanner.db, &id);
-              let id = id.as_ref().to_vec();
-              if seen || scanner.ram_outputs.contains(&id) {
-                panic!("scanned an output multiple times");
-              }
-              scanner.ram_outputs.insert(id);
-            }
-
-            // Clone network because we can't borrow it while also mutably borrowing the
-            // eventualities
-            // Thankfully, network is written to be a cheap clone
-            let network = scanner.network.clone();
-            // TODO: This get_eventuality_completions call will panic if called multiple times over
-            // the same blocks (such as when checking multiple keys under the current layout),
-            // as get_eventuality_completions assumes it's always only fed a future block
-            for (id, tx) in
-              network.get_eventuality_completions(&mut scanner.eventualities, &block).await
-            {
-              // This should only happen if there's a P2P net desync or there's a malicious
-              // validator
-              warn!(
-                "eventuality {} resolved by {}, as found on chain. this should not happen",
-                hex::encode(id),
-                hex::encode(&tx)
-              );
-
-              if !scanner.emit(ScannerEvent::Completed(id, tx)) {
-                return;
-              }
-            }
-
-            // Don't emit an event if there's not any outputs
-            if outputs.is_empty() {
-              continue;
-            }
-
-            // Save the outputs to disk
-            let mut txn = scanner.db.txn();
-            ScannerDb::<N, D>::save_outputs(&mut txn, &key, &block_id, &outputs);
-            txn.commit();
-
-            // Send all outputs
-            // TODO2: Fire this with all outputs for all keys, not for each key
-            if !scanner.emit(ScannerEvent::Block { block: block_id, outputs }) {
-              return;
-            }
-          }
-        }
-      }
-    }
-  }
-}

processor/src/signer.rs

@@ -139,10 +139,6 @@ impl<N: Network, D: Db> Signer<N, D> {
     }
   }
 
-  pub fn keys(&self) -> ThresholdKeys<N::Curve> {
-    self.keys.clone()
-  }
-
   fn verify_id(&self, id: &SignId) -> Result<(), ()> {
     // Check the attempt lines up
     match self.attempt.get(&id.id) {
@@ -202,28 +198,42 @@ impl<N: Network, D: Db> Signer<N, D> {
     self.events.push_back(SignerEvent::SignedTransaction { id, tx: tx_id });
   }
 
-  pub async fn eventuality_completion(
+  pub fn completed(&mut self, txn: &mut D::Transaction<'_>, id: [u8; 32], tx: N::Transaction) {
+    let first_completion = !self.already_completed(txn, id);
+
+    // Save this completion to the DB
+    SignerDb::<N, D>::save_transaction(txn, &tx);
+    SignerDb::<N, D>::complete(txn, id, &tx.id());
+
+    if first_completion {
+      self.complete(id, tx.id());
+    }
+  }
+
+  // Doesn't use any loops/retries since we'll eventually get this from the Scanner anyways
+  async fn claimed_eventuality_completion(
     &mut self,
     txn: &mut D::Transaction<'_>,
     id: [u8; 32],
     tx_id: &<N::Transaction as Transaction<N>>::Id,
-  ) {
+  ) -> bool {
     if let Some(eventuality) = SignerDb::<N, D>::eventuality(txn, id) {
       // Transaction hasn't hit our mempool/was dropped for a different signature
       // The latter can happen given certain latency conditions/a single malicious signer
-      // In the case of a single malicious signer, they can drag multiple honest
+      // In the case of a single malicious signer, they can drag multiple honest validators down
-      // validators down with them, so we unfortunately can't slash on this case
+      // with them, so we unfortunately can't slash on this case
       let Ok(tx) = self.network.get_transaction(tx_id).await else {
         warn!(
-          "a validator claimed {} completed {} yet we didn't have that TX in our mempool",
+          "a validator claimed {} completed {} yet we didn't have that TX in our mempool {}",
           hex::encode(tx_id),
           hex::encode(id),
+          "(or had another connectivity issue)",
         );
-        return;
+        return false;
       };
 
       if self.network.confirm_completion(&eventuality, &tx) {
-        info!("eventuality for {} resolved in TX {}", hex::encode(id), hex::encode(tx_id));
+        info!("signer eventuality for {} resolved in TX {}", hex::encode(id), hex::encode(tx_id));
 
         let first_completion = !self.already_completed(txn, id);
 
@@ -233,6 +243,7 @@ impl<N: Network, D: Db> Signer<N, D> {
 
         if first_completion {
           self.complete(id, tx.id());
+          return true;
         }
       } else {
         warn!(
@@ -242,12 +253,17 @@ impl<N: Network, D: Db> Signer<N, D> {
         );
       }
     } else {
-      warn!(
+      // If we don't have this in RAM, it should be because we already finished signing it
-        "signer {} informed of the completion of plan {}. that plan was not recognized",
+      // TODO: Will the coordinator ever send us Completed for an unknown ID?
+      assert!(SignerDb::<N, D>::completed(txn, id).is_some());
+      info!(
+        "signer {} informed of the eventuality completion for plan {}, {}",
         hex::encode(self.keys.group_key().to_bytes()),
         hex::encode(id),
+        "which we already marked as completed",
       );
     }
+    false
   }
 
   async fn attempt(&mut self, txn: &mut D::Transaction<'_>, id: [u8; 32], attempt: u32) {
@@ -311,7 +327,7 @@ impl<N: Network, D: Db> Signer<N, D> {
     SignerDb::<N, D>::attempt(txn, &id);
 
     // Attempt to create the TX
-    let machine = match self.network.attempt_send(tx).await {
+    let machine = match self.network.attempt_send(self.keys.clone(), tx).await {
       Err(e) => {
         error!("failed to attempt {}, #{}: {:?}", hex::encode(id.id), id.attempt, e);
         return;
@@ -481,7 +497,7 @@ impl<N: Network, D: Db> Signer<N, D> {
         }
         tx.as_mut().copy_from_slice(&tx_vec);
 
-        self.eventuality_completion(txn, id, &tx).await;
+        self.claimed_eventuality_completion(txn, id, &tx).await;
       }
     }
   }

processor/src/substrate_signer.rs

@@ -208,7 +208,7 @@ impl<D: Db> SubstrateSigner<D> {
     // b"substrate" is a literal from sp-core
     let machine = AlgorithmMachine::new(Schnorrkel::new(b"substrate"), self.keys.clone());
 
-    // TODO: Use a seeded RNG here so we don't produce distinct messages with the same purpose
+    // TODO: Use a seeded RNG here so we don't produce distinct messages with the same intent
     // This is also needed so we don't preprocess, send preprocess, reboot before ack'ing the
     // message, send distinct preprocess, and then attempt a signing session premised on the former
     // with the latter

processor/src/tests/addresses.rs

@@ -12,11 +12,12 @@ use serai_db::{DbTxn, MemDb};
 use crate::{
   Plan, Db,
   networks::{OutputType, Output, Block, Network},
-  scanner::{ScannerEvent, Scanner, ScannerHandle},
+  multisigs::scanner::{ScannerEvent, Scanner, ScannerHandle},
   tests::sign,
 };
 
 async fn spend<N: Network, D: Db>(
+  db: &mut D,
   network: &N,
   keys: &HashMap<Participant, ThresholdKeys<N::Curve>>,
   scanner: &mut ScannerHandle<N, D>,
@@ -32,10 +33,14 @@ async fn spend<N: Network, D: Db>(
         keys.clone(),
         network
           .prepare_send(
-            keys.clone(),
             network.get_latest_block_number().await.unwrap() - N::CONFIRMATIONS,
             // Send to a change output
-            Plan { key, inputs: outputs.clone(), payments: vec![], change: Some(key) },
+            Plan {
+              key,
+              inputs: outputs.clone(),
+              payments: vec![],
+              change: Some(N::change_address(key)),
+            },
             network.get_fee().await,
           )
           .await
@@ -51,13 +56,19 @@ async fn spend<N: Network, D: Db>(
     network.mine_block().await;
   }
   match timeout(Duration::from_secs(30), scanner.events.recv()).await.unwrap().unwrap() {
-    ScannerEvent::Block { block: _, outputs } => {
+    ScannerEvent::Block { is_retirement_block, block, outputs } => {
+      scanner.multisig_completed.send(false).unwrap();
+      assert!(!is_retirement_block);
       assert_eq!(outputs.len(), 1);
       // Make sure this is actually a change output
       assert_eq!(outputs[0].kind(), OutputType::Change);
+      let mut txn = db.txn();
+      assert_eq!(scanner.ack_block(&mut txn, block).await.1, outputs);
+      scanner.release_lock().await;
+      txn.commit();
       outputs
     }
-    ScannerEvent::Completed(_, _) => {
+    ScannerEvent::Completed(_, _, _, _) => {
       panic!("unexpectedly got eventuality completion");
     }
   }
@@ -76,11 +87,14 @@ pub async fn test_addresses<N: Network>(network: N) {
   }
 
   let mut db = MemDb::new();
-  let (mut scanner, active_keys) = Scanner::new(network.clone(), db.clone());
+  let (mut scanner, current_keys) = Scanner::new(network.clone(), db.clone());
-  assert!(active_keys.is_empty());
+  assert!(current_keys.is_empty());
   let mut txn = db.txn();
-  scanner.rotate_key(&mut txn, network.get_latest_block_number().await.unwrap(), key).await;
+  scanner.register_key(&mut txn, network.get_latest_block_number().await.unwrap(), key).await;
   txn.commit();
+  for _ in 0 .. N::CONFIRMATIONS {
+    network.mine_block().await;
+  }
 
   // Receive funds to the branch address and make sure it's properly identified
   let block_id = network.test_send(N::branch_address(key)).await.id();
@@ -88,19 +102,25 @@ pub async fn test_addresses<N: Network>(network: N) {
   // Verify the Scanner picked them up
   let outputs =
     match timeout(Duration::from_secs(30), scanner.events.recv()).await.unwrap().unwrap() {
-      ScannerEvent::Block { block, outputs } => {
+      ScannerEvent::Block { is_retirement_block, block, outputs } => {
+        scanner.multisig_completed.send(false).unwrap();
+        assert!(!is_retirement_block);
         assert_eq!(block, block_id);
         assert_eq!(outputs.len(), 1);
         assert_eq!(outputs[0].kind(), OutputType::Branch);
+        let mut txn = db.txn();
+        assert_eq!(scanner.ack_block(&mut txn, block).await.1, outputs);
+        scanner.release_lock().await;
+        txn.commit();
         outputs
       }
-      ScannerEvent::Completed(_, _) => {
+      ScannerEvent::Completed(_, _, _, _) => {
         panic!("unexpectedly got eventuality completion");
       }
     };
 
   // Spend the branch output, creating a change output and ensuring we actually get change
-  let outputs = spend(&network, &keys, &mut scanner, outputs).await;
+  let outputs = spend(&mut db, &network, &keys, &mut scanner, outputs).await;
   // Also test spending the change output
-  spend(&network, &keys, &mut scanner, outputs).await;
+  spend(&mut db, &network, &keys, &mut scanner, outputs).await;
 }

processor/src/tests/literal/mod.rs

@@ -16,6 +16,7 @@ mod bitcoin {
     bitcoin_signer,
     bitcoin_wallet,
     bitcoin_addresses,
+    bitcoin_no_deadlock_in_multisig_completed,
   );
 }
 
@@ -39,5 +40,6 @@ mod monero {
     monero_signer,
     monero_wallet,
     monero_addresses,
+    monero_no_deadlock_in_multisig_completed,
   );
 }

processor/src/tests/mod.rs

@@ -2,7 +2,7 @@ mod key_gen;
 pub(crate) use key_gen::test_key_gen;
 
 mod scanner;
-pub(crate) use scanner::test_scanner;
+pub(crate) use scanner::{test_scanner, test_no_deadlock_in_multisig_completed};
 
 mod signer;
 pub(crate) use signer::{sign, test_signer};
@@ -59,8 +59,12 @@ macro_rules! test_network {
     $signer: ident,
     $wallet: ident,
     $addresses: ident,
+    $no_deadlock_in_multisig_completed: ident,
   ) => {
-    use $crate::tests::{test_key_gen, test_scanner, test_signer, test_wallet, test_addresses};
+    use $crate::tests::{
+      test_key_gen, test_scanner, test_no_deadlock_in_multisig_completed, test_signer, test_wallet,
+      test_addresses,
+    };
 
     // This doesn't interact with a node and accordingly doesn't need to be run sequentially
     #[tokio::test]
@@ -93,6 +97,12 @@ macro_rules! test_network {
         test_addresses($network().await).await;
       }
     }
+
+    async_sequential! {
+      async fn $no_deadlock_in_multisig_completed() {
+        test_no_deadlock_in_multisig_completed($network().await).await;
+      }
+    }
   };
 }
 

processor/src/tests/scanner.rs

@@ -3,17 +3,15 @@ use std::sync::{Arc, Mutex};
 
 use rand_core::OsRng;
 
-use frost::Participant;
+use frost::{Participant, tests::key_gen};
 
 use tokio::time::timeout;
 
-use serai_client::primitives::BlockHash;
-
 use serai_db::{DbTxn, Db, MemDb};
 
 use crate::{
   networks::{OutputType, Output, Block, Network},
-  scanner::{ScannerEvent, Scanner, ScannerHandle},
+  multisigs::scanner::{ScannerEvent, Scanner, ScannerHandle},
 };
 
 pub async fn test_scanner<N: Network>(network: N) {
@@ -32,16 +30,19 @@ pub async fn test_scanner<N: Network>(network: N) {
   let db = MemDb::new();
   let new_scanner = || async {
     let mut db = db.clone();
-    let (mut scanner, active_keys) = Scanner::new(network.clone(), db.clone());
+    let (mut scanner, current_keys) = Scanner::new(network.clone(), db.clone());
     let mut first = first.lock().unwrap();
     if *first {
-      assert!(active_keys.is_empty());
+      assert!(current_keys.is_empty());
       let mut txn = db.txn();
-      scanner.rotate_key(&mut txn, activation_number, group_key).await;
+      scanner.register_key(&mut txn, activation_number, group_key).await;
       txn.commit();
+      for _ in 0 .. N::CONFIRMATIONS {
+        network.mine_block().await;
+      }
       *first = false;
     } else {
-      assert_eq!(active_keys.len(), 1);
+      assert_eq!(current_keys.len(), 1);
     }
     scanner
   };
@@ -55,13 +56,15 @@ pub async fn test_scanner<N: Network>(network: N) {
   let verify_event = |mut scanner: ScannerHandle<N, MemDb>| async {
     let outputs =
       match timeout(Duration::from_secs(30), scanner.events.recv()).await.unwrap().unwrap() {
-        ScannerEvent::Block { block, outputs } => {
+        ScannerEvent::Block { is_retirement_block, block, outputs } => {
+          scanner.multisig_completed.send(false).unwrap();
+          assert!(!is_retirement_block);
           assert_eq!(block, block_id);
           assert_eq!(outputs.len(), 1);
           assert_eq!(outputs[0].kind(), OutputType::External);
           outputs
         }
-        ScannerEvent::Completed(_, _) => {
+        ScannerEvent::Completed(_, _, _, _) => {
           panic!("unexpectedly got eventuality completion");
         }
       };
@@ -73,22 +76,10 @@ pub async fn test_scanner<N: Network>(network: N) {
   verify_event(new_scanner().await).await;
 
   // Acknowledge the block
-
-  // Acknowledging it should yield a list of all blocks since the last acknowledged block
-  let mut blocks = vec![];
-  let mut curr_block = activation_number + 1;
-  loop {
-    let block = network.get_block(curr_block).await.unwrap().id();
-    blocks.push(BlockHash(block.as_ref().try_into().unwrap()));
-    if block == block_id {
-      break;
-    }
-    curr_block += 1;
-  }
-
   let mut cloned_db = db.clone();
   let mut txn = cloned_db.txn();
-  assert_eq!(scanner.ack_up_to_block(&mut txn, keys.group_key(), block_id).await, outputs);
+  assert_eq!(scanner.ack_block(&mut txn, block_id).await.1, outputs);
+  scanner.release_lock().await;
   txn.commit();
 
   // There should be no more events
@@ -97,3 +88,67 @@ pub async fn test_scanner<N: Network>(network: N) {
   // Create a new scanner off the current DB and make sure it also does nothing
   assert!(timeout(Duration::from_secs(30), new_scanner().await.events.recv()).await.is_err());
 }
+
+pub async fn test_no_deadlock_in_multisig_completed<N: Network>(network: N) {
+  // Mine blocks so there's a confirmed block
+  for _ in 0 .. N::CONFIRMATIONS {
+    network.mine_block().await;
+  }
+
+  let mut db = MemDb::new();
+  let (mut scanner, current_keys) = Scanner::new(network.clone(), db.clone());
+  assert!(current_keys.is_empty());
+
+  let mut txn = db.txn();
+  // Register keys to cause Block events at CONFIRMATIONS (dropped since first keys),
+  // CONFIRMATIONS + 1, and CONFIRMATIONS + 2
+  for i in 0 .. 3 {
+    scanner
+      .register_key(
+        &mut txn,
+        network.get_latest_block_number().await.unwrap() + N::CONFIRMATIONS + i,
+        {
+          let mut keys = key_gen(&mut OsRng);
+          for (_, keys) in keys.iter_mut() {
+            N::tweak_keys(keys);
+          }
+          keys[&Participant::new(1).unwrap()].group_key()
+        },
+      )
+      .await;
+  }
+  txn.commit();
+
+  for _ in 0 .. (3 * N::CONFIRMATIONS) {
+    network.mine_block().await;
+  }
+
+  let block_id =
+    match timeout(Duration::from_secs(30), scanner.events.recv()).await.unwrap().unwrap() {
+      ScannerEvent::Block { is_retirement_block, block, outputs: _ } => {
+        scanner.multisig_completed.send(false).unwrap();
+        assert!(!is_retirement_block);
+        block
+      }
+      ScannerEvent::Completed(_, _, _, _) => {
+        panic!("unexpectedly got eventuality completion");
+      }
+    };
+
+  match timeout(Duration::from_secs(30), scanner.events.recv()).await.unwrap().unwrap() {
+    ScannerEvent::Block { .. } => {}
+    ScannerEvent::Completed(_, _, _, _) => {
+      panic!("unexpectedly got eventuality completion");
+    }
+  };
+
+  // The ack_block acquisiton shows the Scanner isn't maintaining the lock on its own thread after
+  // emitting the Block event
+  // TODO: This is incomplete. Also test after emitting Completed
+  let mut txn = db.txn();
+  assert_eq!(scanner.ack_block(&mut txn, block_id).await.1, vec![]);
+  scanner.release_lock().await;
+  txn.commit();
+
+  scanner.multisig_completed.send(false).unwrap();
+}

processor/src/tests/signer.rs

@@ -153,7 +153,7 @@ pub async fn test_signer<N: Network>(network: N) {
   }
   let key = keys[&Participant::new(1).unwrap()].group_key();
 
-  let outputs = network.get_outputs(&network.test_send(N::address(key)).await, key).await.unwrap();
+  let outputs = network.get_outputs(&network.test_send(N::address(key)).await, key).await;
   let sync_block = network.get_latest_block_number().await.unwrap() - N::CONFIRMATIONS;
   let fee = network.get_fee().await;
 
@@ -163,13 +163,12 @@ pub async fn test_signer<N: Network>(network: N) {
   for (i, keys) in keys.drain() {
     let (signable, eventuality) = network
       .prepare_send(
-        keys.clone(),
         sync_block,
         Plan {
           key,
           inputs: outputs.clone(),
           payments: vec![Payment { address: N::address(key), data: None, amount }],
-          change: Some(key),
+          change: Some(N::change_address(key)),
         },
         fee,
       )
@@ -194,8 +193,7 @@ pub async fn test_signer<N: Network>(network: N) {
       &network.get_block(network.get_latest_block_number().await.unwrap()).await.unwrap(),
       key,
     )
-    .await
+    .await;
-    .unwrap();
   assert_eq!(outputs.len(), 2);
   // Adjust the amount for the fees
   let amount = amount - tx.fee(&network).await;

processor/src/tests/wallet.rs

@@ -11,13 +11,20 @@ use serai_db::{DbTxn, Db, MemDb};
 use crate::{
   Payment, Plan,
   networks::{Output, Transaction, Block, Network},
-  scanner::{ScannerEvent, Scanner},
+  multisigs::{
-  scheduler::Scheduler,
+    scanner::{ScannerEvent, Scanner},
+    scheduler::Scheduler,
+  },
   tests::sign,
 };
 
 // Tests the Scanner, Scheduler, and Signer together
 pub async fn test_wallet<N: Network>(network: N) {
+  // Mine blocks so there's a confirmed block
+  for _ in 0 .. N::CONFIRMATIONS {
+    network.mine_block().await;
+  }
+
   let mut keys = key_gen(&mut OsRng);
   for (_, keys) in keys.iter_mut() {
     N::tweak_keys(keys);
@@ -25,27 +32,36 @@ pub async fn test_wallet<N: Network>(network: N) {
   let key = keys[&Participant::new(1).unwrap()].group_key();
 
   let mut db = MemDb::new();
-  let (mut scanner, active_keys) = Scanner::new(network.clone(), db.clone());
+  let (mut scanner, current_keys) = Scanner::new(network.clone(), db.clone());
-  assert!(active_keys.is_empty());
+  assert!(current_keys.is_empty());
   let (block_id, outputs) = {
     let mut txn = db.txn();
-    scanner.rotate_key(&mut txn, network.get_latest_block_number().await.unwrap(), key).await;
+    scanner.register_key(&mut txn, network.get_latest_block_number().await.unwrap(), key).await;
     txn.commit();
+    for _ in 0 .. N::CONFIRMATIONS {
+      network.mine_block().await;
+    }
 
     let block = network.test_send(N::address(key)).await;
     let block_id = block.id();
 
     match timeout(Duration::from_secs(30), scanner.events.recv()).await.unwrap().unwrap() {
-      ScannerEvent::Block { block, outputs } => {
+      ScannerEvent::Block { is_retirement_block, block, outputs } => {
+        scanner.multisig_completed.send(false).unwrap();
+        assert!(!is_retirement_block);
         assert_eq!(block, block_id);
         assert_eq!(outputs.len(), 1);
         (block_id, outputs)
       }
-      ScannerEvent::Completed(_, _) => {
+      ScannerEvent::Completed(_, _, _, _) => {
         panic!("unexpectedly got eventuality completion");
       }
     }
   };
+  let mut txn = db.txn();
+  assert_eq!(scanner.ack_block(&mut txn, block_id.clone()).await.1, outputs);
+  scanner.release_lock().await;
+  txn.commit();
 
   let mut txn = db.txn();
   let mut scheduler = Scheduler::new::<MemDb>(&mut txn, key);
@@ -54,6 +70,8 @@ pub async fn test_wallet<N: Network>(network: N) {
     &mut txn,
     outputs.clone(),
     vec![Payment { address: N::address(key), data: None, amount }],
+    key,
+    false,
   );
   txn.commit();
   assert_eq!(
@@ -62,7 +80,7 @@ pub async fn test_wallet<N: Network>(network: N) {
       key,
       inputs: outputs.clone(),
       payments: vec![Payment { address: N::address(key), data: None, amount }],
-      change: Some(key),
+      change: Some(N::change_address(key)),
     }]
   );
 
@@ -78,7 +96,7 @@ pub async fn test_wallet<N: Network>(network: N) {
   let mut eventualities = vec![];
   for (i, keys) in keys.drain() {
     let (signable, eventuality) = network
-      .prepare_send(keys.clone(), network.get_block_number(&block_id).await, plans[0].clone(), fee)
+      .prepare_send(network.get_block_number(&block_id).await, plans[0].clone(), fee)
       .await
       .unwrap()
       .0
@@ -93,8 +111,7 @@ pub async fn test_wallet<N: Network>(network: N) {
   network.mine_block().await;
   let block_number = network.get_latest_block_number().await.unwrap();
   let block = network.get_block(block_number).await.unwrap();
-  let first_outputs = outputs;
+  let outputs = network.get_outputs(&block, key).await;
-  let outputs = network.get_outputs(&block, key).await.unwrap();
   assert_eq!(outputs.len(), 2);
   let amount = amount - tx.fee(&network).await;
   assert!((outputs[0].amount() == amount) || (outputs[1].amount() == amount));
@@ -108,20 +125,20 @@ pub async fn test_wallet<N: Network>(network: N) {
   }
 
   match timeout(Duration::from_secs(30), scanner.events.recv()).await.unwrap().unwrap() {
-    ScannerEvent::Block { block: block_id, outputs: these_outputs } => {
+    ScannerEvent::Block { is_retirement_block, block: block_id, outputs: these_outputs } => {
+      scanner.multisig_completed.send(false).unwrap();
+      assert!(!is_retirement_block);
       assert_eq!(block_id, block.id());
       assert_eq!(these_outputs, outputs);
     }
-    ScannerEvent::Completed(_, _) => {
+    ScannerEvent::Completed(_, _, _, _) => {
       panic!("unexpectedly got eventuality completion");
     }
   }
 
   // Check the Scanner DB can reload the outputs
   let mut txn = db.txn();
-  assert_eq!(
+  assert_eq!(scanner.ack_block(&mut txn, block.id()).await.1, outputs);
-    scanner.ack_up_to_block(&mut txn, key, block.id()).await,
+  scanner.release_lock().await;
-    [first_outputs, outputs].concat().to_vec()
-  );
   txn.commit();
 }

tests/coordinator/src/tests/batch.rs

@@ -22,10 +22,9 @@ use messages::{sign::SignId, SubstrateContext, CoordinatorMessage};
 
 use crate::{*, tests::*};
 
-pub async fn batch<C: Ciphersuite>(
+pub async fn batch(
   processors: &mut [Processor],
   substrate_key: &Zeroizing<<Ristretto as Ciphersuite>::F>,
-  network_key: &Zeroizing<C::F>,
   batch: Batch,
 ) -> u64 {
   let mut id = [0; 32];
@@ -213,7 +212,6 @@ pub async fn batch<C: Ciphersuite>(
           },
           network: batch.batch.network,
           block: last_serai_block,
-          key: (C::generator() * **network_key).to_bytes().as_ref().to_vec(),
           burns: vec![],
           batches: vec![batch.batch.id],
         }
@@ -257,11 +255,10 @@ async fn batch_test() {
       }
       let mut processors = new_processors;
 
-      let (substrate_key, network_key) = key_gen::<Secp256k1>(&mut processors).await;
+      let (substrate_key, _) = key_gen::<Secp256k1>(&mut processors).await;
-      batch::<Secp256k1>(
+      batch(
         &mut processors,
         &substrate_key,
-        &network_key,
         Batch {
           network: NetworkId::Bitcoin,
           id: 0,

tests/coordinator/src/tests/sign.rs

@@ -232,10 +232,9 @@ async fn sign_test() {
       let balance = Balance { coin: Coin::Bitcoin, amount };
 
       let coin_block = BlockHash([0x33; 32]);
-      let block_included_in = batch::<Secp256k1>(
+      let block_included_in = batch(
         &mut processors,
         &substrate_key,
-        &network_key,
         Batch {
           network: NetworkId::Bitcoin,
           id: 0,
@@ -346,7 +345,6 @@ async fn sign_test() {
               },
               network: NetworkId::Bitcoin,
               block: last_serai_block.number(),
-              key: (Secp256k1::generator() * *network_key).to_bytes().to_vec(),
               burns: vec![OutInstructionWithBalance {
                 instruction: out_instruction.clone(),
                 balance: Balance { coin: Coin::Bitcoin, amount }

tests/message-queue/src/lib.rs

@@ -47,6 +47,7 @@ pub fn instance(
         hex::encode((Ristretto::generator() * priv_keys[&NetworkId::Monero]).to_bytes()),
       ),
       ("DB_PATH".to_string(), "./message-queue-db".to_string()),
+      ("RUST_LOG".to_string(), "serai_message_queue=trace,".to_string()),
     ]
     .into(),
   );

tests/processor/src/lib.rs

@@ -54,6 +54,7 @@ pub fn processor_instance(
       ("NETWORK_RPC_LOGIN".to_string(), format!("{RPC_USER}:{RPC_PASS}")),
       ("NETWORK_RPC_PORT".to_string(), port.to_string()),
       ("DB_PATH".to_string(), "./processor-db".to_string()),
+      ("RUST_LOG".to_string(), "serai_processor=trace,".to_string()),
     ]
     .into(),
   )

tests/processor/src/tests/batch.rs

@@ -149,7 +149,6 @@ pub(crate) async fn substrate_block(
       context: _,
       network: sent_network,
       block: sent_block,
-      key: _,
       burns: _,
       batches: _,
     } => {
@@ -280,8 +279,6 @@ fn batch_test() {
               },
               network,
               block: substrate_block_num + u64::from(i),
-              // TODO: Should we use the network key here? Or should we only use the Ristretto key?
-              key: key_pair.1.to_vec(),
               burns: vec![],
               batches: vec![batch.batch.id],
             },

tests/processor/src/tests/send.rs

@@ -213,8 +213,6 @@ fn send_test() {
             },
             network,
             block: substrate_block_num,
-            // TODO: Should we use the network key here? Or should we only use the Ristretto key?
-            key: key_pair.1.to_vec(),
             burns: vec![OutInstructionWithBalance {
               instruction: OutInstruction { address: wallet.address(), data: None },
               balance: balance_sent,