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* Upstream GBP, divisor, circuit abstraction, and EC gadgets from FCMP++ * Initial eVRF implementation Not quite done yet. It needs to communicate the resulting points and proofs to extract them from the Pedersen Commitments in order to return those, and then be tested. * Add the openings of the PCs to the eVRF as necessary * Add implementation of secq256k1 * Make DKG Encryption a bit more flexible No longer requires the use of an EncryptionKeyMessage, and allows pre-defined keys for encryption. * Make NUM_BITS an argument for the field macro * Have the eVRF take a Zeroizing private key * Initial eVRF-based DKG * Add embedwards25519 curve * Inline the eVRF into the DKG library Due to how we're handling share encryption, we'd either need two circuits or to dedicate this circuit to the DKG. The latter makes sense at this time. * Add documentation to the eVRF-based DKG * Add paragraph claiming robustness * Update to the new eVRF proof * Finish routing the eVRF functionality Still needs errors and serialization, along with a few other TODOs. * Add initial eVRF DKG test * Improve eVRF DKG Updates how we calculcate verification shares, improves performance when extracting multiple sets of keys, and adds more to the test for it. * Start using a proper error for the eVRF DKG * Resolve various TODOs Supports recovering multiple key shares from the eVRF DKG. Inlines two loops to save 2**16 iterations. Adds support for creating a constant time representation of scalars < NUM_BITS. * Ban zero ECDH keys, document non-zero requirements * Implement eVRF traits, all the way up to the DKG, for secp256k1/ed25519 * Add Ristretto eVRF trait impls * Support participating multiple times in the eVRF DKG * Only participate once per key, not once per key share * Rewrite processor key-gen around the eVRF DKG Still a WIP. * Finish routing the new key gen in the processor Doesn't touch the tests, coordinator, nor Substrate yet. `cargo +nightly fmt && cargo +nightly-2024-07-01 clippy --all-features -p serai-processor` does pass. * Deduplicate and better document in processor key_gen * Update serai-processor tests to the new key gen * Correct amount of yx coefficients, get processor key gen test to pass * Add embedded elliptic curve keys to Substrate * Update processor key gen tests to the eVRF DKG * Have set_keys take signature_participants, not removed_participants Now no one is removed from the DKG. Only `t` people publish the key however. Uses a BitVec for an efficient encoding of the participants. * Update the coordinator binary for the new DKG This does not yet update any tests. * Add sensible Debug to key_gen::[Processor, Coordinator]Message * Have the DKG explicitly declare how to interpolate its shares Removes the hack for MuSig where we multiply keys by the inverse of their lagrange interpolation factor. * Replace Interpolation::None with Interpolation::Constant Allows the MuSig DKG to keep the secret share as the original private key, enabling deriving FROST nonces consistently regardless of the MuSig context. * Get coordinator tests to pass * Update spec to the new DKG * Get clippy to pass across the repo * cargo machete * Add an extra sleep to ensure expected ordering of `Participation`s * Update orchestration * Remove bad panic in coordinator It expected ConfirmationShare to be n-of-n, not t-of-n. * Improve documentation on functions * Update TX size limit We now no longer have to support the ridiculous case of having 49 DKG participations within a 101-of-150 DKG. It does remain quite high due to needing to _sign_ so many times. It'd may be optimal for parties with multiple key shares to independently send their preprocesses/shares (despite the overhead that'll cause with signatures and the transaction structure). * Correct error in the Processor spec document * Update a few comments in the validator-sets pallet * Send/Recv Participation one at a time Sending all, then attempting to receive all in an expected order, wasn't working even with notable delays between sending messages. This points to the mempool not working as expected... * Correct ThresholdKeys serialization in modular-frost test * Updating existing TX size limit test for the new DKG parameters * Increase time allowed for the DKG on the GH CI * Correct construction of signature_participants in serai-client tests Fault identified by akil. * Further contextualize DkgConfirmer by ValidatorSet Caught by a safety check we wouldn't reuse preprocesses across messages. That raises the question of we were prior reusing preprocesses (reusing keys)? Except that'd have caused a variety of signing failures (suggesting we had some staggered timing avoiding it in practice but yes, this was possible in theory). * Add necessary calls to set_embedded_elliptic_curve_key in coordinator set rotation tests * Correct shimmed setting of a secq256k1 key * cargo fmt * Don't use `[0; 32]` for the embedded keys in the coordinator rotation test The key_gen function expects the random values already decided. * Big-endian secq256k1 scalars Also restores the prior, safer, Encryption::register function.
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Processor
The processor is a service which has an instance spawned per network. It is responsible for several tasks, from scanning an external network to signing transactions with payments.
This document primarily discusses its flow with regards to the coordinator.
Generate Key
On key_gen::CoordinatorMessage::GenerateKey, the processor begins a pair of
instances of the distributed key generation protocol.
The first instance is for a Ristretto public key used to publish data to the Serai blockchain. The second instance is for a key to use on the external network. This pair of DKG instances is considered a single instance of Serai's overall DKG protocol.
The participations in both protocols are sent to the coordinator in
key_gen::ProcessorMessage::Participation messages, individually, as they come
in.
Key Gen Participations
On key_gen::CoordinatorMessage::Participation, the processor stores the
contained participation, verifying participations as sane. Once it receives t
honest participations, the processor completes the DKG and sends the generated
key pair to the coordinator in a key_gen::ProcessorMessage::GeneratedKeyPair.
Confirm Key Pair
On substrate::CoordinatorMessage::ConfirmKeyPair, the processor starts using
the newly confirmed key, scanning blocks on the external network for
transfers to it.
External Network Block
When the external network has a new block, which is considered finalized (either due to being literally finalized or due to having a sufficient amount of confirmations), it's scanned.
Outputs to the key of Serai's multisig are saved to the database. Outputs which
newly transfer into Serai are used to build Batchs for the block. The
processor then begins a threshold signature protocol with its key pair's
Ristretto key to sign the Batchs.
The Batchs are each sent to the coordinator in a
substrate::ProcessorMessage::Batch, enabling the coordinator to know what
Batchs should be published to Serai. After each
substrate::ProcessorMessage::Batch, the preprocess for the first instance of
its signing protocol is sent to the coordinator in a
coordinator::ProcessorMessage::BatchPreprocess.
As a design comment, we may be able to sign now possible, already scheduled, branch/leaf transactions at this point. Doing so would be giving a mutable borrow over the scheduler to both the external network and the Serai network, and would accordingly be unsafe. We may want to look at splitting the scheduler in two, in order to reduce latency (TODO).
Batch Preprocesses
On coordinator::CoordinatorMessage::BatchPreprocesses, the processor
continues the specified batch signing protocol, sending
coordinator::ProcessorMessage::BatchShare to the coordinator.
Batch Shares
On coordinator::CoordinatorMessage::BatchShares, the processor
completes the specified batch signing protocol. If successful, the processor
stops signing for this batch and sends
substrate::ProcessorMessage::SignedBatch to the coordinator.
Batch Re-attempt
On coordinator::CoordinatorMessage::BatchReattempt, the processor will create
a new instance of the batch signing protocol. The new protocol's preprocess is
sent to the coordinator in a coordinator::ProcessorMessage::BatchPreprocess.
Substrate Block
On substrate::CoordinatorMessage::SubstrateBlock, the processor:
- Marks all blocks, up to the external block now considered finalized by Serai, as having had their batches signed.
- Adds the new outputs from newly finalized blocks to the scheduler, along
with the necessary payments from
Burnevents on Serai. - Sends a
substrate::ProcessorMessage::SubstrateBlockAck, containing the IDs of all plans now being signed for, to the coordinator. - Sends
sign::ProcessorMessage::Preprocessfor each plan now being signed for.
Sign Preprocesses
On sign::CoordinatorMessage::Preprocesses, the processor continues the
specified transaction signing protocol, sending sign::ProcessorMessage::Share
to the coordinator.
Sign Shares
On sign::CoordinatorMessage::Shares, the processor completes the specified
transaction signing protocol. If successful, the processor stops signing for
this transaction and publishes the signed transaction. Then,
sign::ProcessorMessage::Completed is sent to the coordinator, to be
broadcasted to all validators so everyone can observe the attempt completed,
producing a signed and published transaction.
Sign Re-attempt
On sign::CoordinatorMessage::Reattempt, the processor will create a new
a new instance of the transaction signing protocol if it hasn't already
completed/observed completion of an instance of the signing protocol. The new
protocol's preprocess is sent to the coordinator in a
sign::ProcessorMessage::Preprocess.
Sign Completed
On sign::CoordinatorMessage::Completed, the processor verifies the included
transaction hash actually refers to an accepted transaction which completes the
plan it was supposed to. If so, the processor stops locally signing for the
transaction, and emits sign::ProcessorMessage::Completed if it hasn't prior.