serai/docs/coordinator/Tributary.md

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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.

Key Gen Shares

DkgShares is created when a processor sends the coordinator key_gen::ProcessorMessage::Shares. When all validators participating in a multisig publish DkgShares, the coordinator sends the processor key_gen::CoordinatorMessage::Shares.

External Block

When TODO, a ExternalBlock transaction is provided. This is used to have the group acknowledge and synchronize around the block, without the overhead of voting in its acknowledgment.

When a ExternalBlock transaction is included, participants are allowed to publish transactions to produce a threshold signature for the block's Batch.

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 ExternalBlock transaction allowing the batch to be signed has already been included on chain.

When t validators have published BatchPreprocess transactions, a coordinator::ProcessorMessage::BatchPreprocesses is sent to the processor.

Batch Share

BatchShare is created when a processor sends the coordinator coordinator::ProcessorMessage::BatchShare. The relevant ExternalBlock 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, a coordinator::ProcessorMessage::BatchShares with the relevant shares 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, a sign::ProcessorMessage::Preprocesses is sent to the processor.

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, a sign::ProcessorMessage::Shares with the relevant shares is sent to the processor.

Re-attempts

The key generation and 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.