Guard

Overview

Guards are off-chain agents that detect fraud and attest to state on many chains. Guards listen for new messages on the Origin chain and create snapshots that contain the state of the Origin contract (provable on the origin chain) and the state of Synchain (which contains provable updates from the gas oracle, a list of agents, etc). Once this snapshot is created, it is posted to Synchain where a notary can attest to its validity or other guards can report fraud.

Responsibilities

• Keep track of state on all chains

• Keep track of snapshots submitted on all chains

• Submit state snapshots to the Origin and Synapse Chains

• Report fraud by other notaries or guards to Origin Chain, Synapse Chain, and Destination chains as fast as possible (first reporter gets the reward here to incentives instant reporting)

• Update the agent statuses on each chain after fraud is reported.

Report Types

Guards can report various different types of fraud listed below.

Fraud type	Agent	Fraud proving	Fraud reporting	Description
Invalid Snapshot	Notary/Guard	verifyStateWithSnapshot	submitStateReportWithSnapshot (N)	Snapshot having State not matching Origin
Invalid Attestation	Notary	verifyAttestation	submitAttestationReport	Attestation that was never created in Summit
Attestation from Invalid Snapshot	Notary	verifyStateWithAttestation	submitStateReportWithAttestation	Attestation having State not matching Origin
Attestation from Invalid Snapshot	Notary	verifyStateWithSnapshotProof	submitStateReportWithSnapshotProof	(Alternative way to prove/report fraud)
Invalid Receipt	Notary	verifyReceipt	submitReceiptReport	Receipt that doesn't match Destination