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EIP-7549
EIP-7549 moves the committee index outside signed attestations, enabling vote aggregation and improving ZK-friendly consensus validation.EIP-7549 optimizes consensus by relocating the committee index, reducing overhead and enhancing efficiency, especially for ZK proofs.

EIP-7549

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What is this EIP about?

EIP-7549 proposes moving the committee index field outside the signed Attestation message in Ethereum's consensus layer to enable aggregation of identical consensus votes.

It aims to reduce computational overhead and improve efficiency in validating consensus rules, particularly benefiting zero-knowledge (ZK) circuits proving Casper FFG consensus.

Why is this EIP needed?

Current attestations in Ethereum's Beacon Chain include a committee index in the signed Attestation message. This makes otherwise identical votes (same block_root, slot, source, and target) produce distinct signatures, which hinders aggregation. This increases computational and storage requirements for validators and ZK circuits.

The EIP pertains to the consensus layer of Ethereum, specifically optimizing Casper FFG (Friendly Finality Gadget) mechanisms. It focuses on gas efficiency, scalability, and cryptographic verification.

What does this EIP propose, and how does it function?

  • Proposal details:
    • Move committee index outside signed Attestation: This eliminates it from the signing root, enabling identical votes to be aggregated more efficiently.
    • Aggregation improvements: Reduces the number of attestations needed for verification from 1,366 to 22 (for 262,144 active validators), a 62x improvement.
    • Beacon block space optimization: Facilitates inclusion of up to 8 slots' worth of votes in a block, compared to 2 currently, improving resilience during network outages.
  • Mechanisms:
    • Execution layer: No changes are needed here.
    • Consensus layer: The committee index field is moved to an outer container, with committee_bits encoding aggregation data.
    • Deprecation: The committee index field in AttestationData is set to zero but preserved to maintain compatibility with other structures like AttesterSlashing.

What are the security implications of this EIP?

  • Potential risks:
    • Mutation over gossip: Malicious actors could mutate the committee index field in gossiped messages, but this would cause signature verification to fail, mitigating cache pollution risks.
    • First block after fork: Post-fork, prior-fork attestations cannot be included, leading to a temporary reduction in FFG votes and potential penalties for last-slot attesters.
  • Mitigations:
    • Strong gossip verification rules prevent malicious mutations (e.g., rejecting invalid signatures).
    • Deliberate design avoids added complexity in handling dual-fork attestations, as the impact is minor.

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