mirror of
https://github.com/serai-dex/serai.git
synced 2024-11-16 17:07:35 +00:00
130 lines
5.4 KiB
Markdown
130 lines
5.4 KiB
Markdown
# Tributary
|
|
|
|
A tributary is a side-chain, created for a specific multisig instance, used
|
|
as a verifiable broadcast layer.
|
|
|
|
## Transactions
|
|
|
|
### Key Gen Commitments
|
|
|
|
`DkgCommitments` is created when a processor sends the coordinator
|
|
`key_gen::ProcessorMessage::Commitments`. When all validators participating in
|
|
a multisig publish `DkgCommitments`, the coordinator sends the processor
|
|
`key_gen::CoordinatorMessage::Commitments`, excluding the processor's own
|
|
commitments.
|
|
|
|
### Key Gen Shares
|
|
|
|
`DkgShares` is created when a processor sends the coordinator
|
|
`key_gen::ProcessorMessage::Shares`. The coordinator additionally includes its
|
|
own pair of MuSig nonces, used in a signing protocol to inform Substrate of the
|
|
key's successful creation.
|
|
|
|
When all validators participating in a multisig publish `DkgShares`, the
|
|
coordinator sends the processor `key_gen::CoordinatorMessage::Shares`, excluding
|
|
the processor's own shares and the MuSig nonces.
|
|
|
|
### Key Gen Confirmation
|
|
|
|
`DkgConfirmed` is created when a processor sends the coordinator
|
|
`key_gen::ProcessorMessage::GeneratedKeyPair`. The coordinator takes the MuSig
|
|
nonces they prior associated with this DKG attempt and publishes their signature
|
|
share.
|
|
|
|
When all validators participating in the multisig publish `DkgConfirmed`, an
|
|
extrinsic calling `validator_sets::pallet::set_keys` is made to confirm the
|
|
keys.
|
|
|
|
Setting the keys on the Serai blockchain as such lets it receive `Batch`s,
|
|
provides a BFT consensus guarantee, and enables accessibility by users. While
|
|
the tributary itself could offer both the BFT consensus guarantee, and
|
|
verifiable accessibility to users, they'd both require users access the
|
|
tributary. Since Substrate must already know the resulting key, there's no value
|
|
to usage of the tributary as-such, as all desired properties are already offered
|
|
by Substrate.
|
|
|
|
Note that the keys are confirmed when Substrate emits a `KeyGen` event,
|
|
regardless of if the Tributary has the expected `DkgConfirmed` transactions.
|
|
|
|
### Batch
|
|
|
|
When *TODO*, a `Batch` transaction is provided. This is used to have the group
|
|
acknowledge and synchronize around a batch, without the overhead of voting in
|
|
its acknowledgment.
|
|
|
|
When a `Batch` transaction is included, participants are allowed to publish
|
|
transactions to produce a threshold signature for the batch synchronized over.
|
|
|
|
### Substrate Block
|
|
|
|
`SubstrateBlock` is provided when the processor sends the coordinator
|
|
`substrate::ProcessorMessage::SubstrateBlockAck`.
|
|
|
|
When a `SubstrateBlock` transaction is included, participants are allowed to
|
|
publish transactions for the signing protocols it causes.
|
|
|
|
### Batch Preprocess
|
|
|
|
`BatchPreprocess` is created when a processor sends the coordinator
|
|
`coordinator::ProcessorMessage::BatchPreprocess` and an `Batch` transaction
|
|
allowing the batch to be signed has already been included on chain.
|
|
|
|
When `t` validators have published `BatchPreprocess` transactions, if the
|
|
coordinator represents one of the first `t` validators to do so, a
|
|
`coordinator::ProcessorMessage::BatchPreprocesses` is sent to the processor,
|
|
excluding the processor's own preprocess.
|
|
|
|
### Batch Share
|
|
|
|
`BatchShare` is created when a processor sends the coordinator
|
|
`coordinator::ProcessorMessage::BatchShare`. The relevant `Batch`
|
|
transaction having already been included on chain follows from
|
|
`coordinator::ProcessorMessage::BatchShare` being a response to a message which
|
|
also has that precondition.
|
|
|
|
When the `t` validators who first published `BatchPreprocess` transactions have
|
|
published `BatchShare` transactions, if the coordinator represents one of the
|
|
first `t` validators to do so, a `coordinator::ProcessorMessage::BatchShares`
|
|
with the relevant shares (excluding the processor's own) is sent to the
|
|
processor.
|
|
|
|
### Sign Preprocess
|
|
|
|
`SignPreprocess` is created when a processor sends the coordinator
|
|
`sign::ProcessorMessage::Preprocess` and a `SubstrateBlock` transaction
|
|
allowing the transaction to be signed has already been included on chain.
|
|
|
|
When `t` validators have published `SignPreprocess` transactions, if the
|
|
coordinator represents one of the first `t` validators to do so, a
|
|
`sign::ProcessorMessage::Preprocesses` is sent to the processor,
|
|
excluding the processor's own preprocess.
|
|
|
|
### Sign Share
|
|
|
|
`SignShare` is created when a processor sends the coordinator
|
|
`sign::ProcessorMessage::Share`. The relevant `SubstrateBlock` transaction
|
|
having already been included on chain follows from
|
|
`sign::ProcessorMessage::Share` being a response to a message which
|
|
also has that precondition.
|
|
|
|
When the `t` validators who first published `SignPreprocess` transactions have
|
|
published `SignShare` transactions, if the coordinator represents one of the
|
|
first `t` validators to do so, a `sign::ProcessorMessage::Shares` with the
|
|
relevant shares (excluding the processor's own) is sent to the processor.
|
|
|
|
### Sign Completed
|
|
|
|
`SignCompleted` is created when a processor sends the coordinator
|
|
`sign::ProcessorMessage::Completed`. As soon as 34% of validators send
|
|
`Completed`, the signing protocol is no longer further attempted.
|
|
|
|
## Re-attempts
|
|
|
|
Key generation protocols may fail if a validator is malicious. Signing
|
|
protocols, whether batch or transaction, may fail if a validator goes offline or
|
|
takes too long to respond. Accordingly, the tributary will schedule re-attempts.
|
|
These are communicated with `key_gen::CoordinatorMessage::GenerateKey`,
|
|
`coordinator::CoordinatorMessage::BatchReattempt`, and
|
|
`sign::CoordinatorMessage::Reattempt`.
|
|
|
|
TODO: Document the re-attempt scheduling logic.
|