Fraud proof communication about mev-boost HOT 1 OPEN

The design I initially proposed was 3) where mev-boost can call relay_getRelayStatusV1 on the relays to obtain fraud proofs for the last 64 blocks. Main reason for selecting this approach is to avoid needing to solve spam prevention on p2p.

Why I think 3) can work:

• relays have incentive to report against on each other because they can take down a different relay
• it allows all validators to obtain a fraud proof and disconnect from a relay simultaneously
• if a relay provides an invalid fraud proof or spam, they can be punished by mev-boost

The fraud proof does assume that the execution client provides an RPC for simulating a block on top of the state of any of the past 64 blocks. Initially, the plan was to use engine_executePayloadV1 for this, but as I understand it was removed from the engine API and must be replaced.

Validation

sequenceDiagram
    Title: Fraud Proof
    participant mev_boost
    participant relays
    mev_boost->>relays: relay_getRelayStatusV1
    Note over mev_boost: blacklist bad relay

1. if a relay identifies a payload which violates consensus rules and was subsequently proposed to the network, they must craft a FraudProof which contains the necessary information to verify the missbehavior.
2. mev-boost requests recent fraud proofs by calling relay_getRelayStatusV1 on connected relays.
3. If a fraud proof is returned, mev-boost extracts the identity of the offending relay from the payload signature and verifies that the signature matches the payload header.
4. mev-boost calls engine_executePayloadV1 against the local execution client using the payload data provided in the fraud proof. If the response is "INVALID", mev-boost immediately blacklists the relay that generated this payload.
5. the operator must manually remove the offending relay from the blacklist in order to resume receiving payloads.

relay_getRelayStatusV1

Request

• method: relay_getRelayStatusV1

Response

• result: RelayStatus
• error: code and message set in case an exception happens while performing the request.

RelayStatus

• currentState: ForkchoiceStateV1 - current state of the chain seen by the relay.
• nextPayload: PayloadAttributesV1 - attributes of the upcoming payload.
• fraudProofs: Array of FraudProof - any fraud proof produced in the last 64 blocks.

FraudProof

• payloadHeader: SignedMEVPayloadHeader - the invalid payload header signed by the offending relay.
• payload: ExecutionPayloadV1 - the invalid payload revealed to the network.
• block: SignedBlindedBeaconBlock - the invalid beacon block signed and proposed by the validator.

from mev-boost.