ERC-8084: Zero-knowledge proof metadata

ERCs
1

Discussion topic for ERC-8084
Original PR

Update Log

  • 2025-11-10: initial draft

External Reviews

None as of 2025-11-10.

Outstanding Issues

None as of 2025-11-10.

Summary

ZKMeta proposes a minimal, universal metadata interface for any Ethereum contract that verifies or consumes zero-knowledge proofs. Rather than standardizing proof formats, it standardizes the accompanying metadata required by tooling, wallets, explorers, relayers, and cross-chain systems to correctly interpret and validate proofs.

ZKMeta exposes the following components:

  • proof system identifier (Groth16, Plonk, Halo2, zkVM, etc.)
  • circuit identifier (content-addressed hash of the circuit artifact)
  • circuit version (semver-encoded uint64)
  • public-inputs schema hash
  • public-inputs schema URI (content-addressed or hash-suffixed HTTPS)
  • verification-key URI (content-addressed or hash-suffixed HTTPS)

This creates a foundation for a standardized “ZK ABI” layer that is needed across the ecosystem.

Purpose of This Standard

ZK integration today is fragmented:

  • No standard way to identify proof systems
  • No versioning convention for circuits
  • No uniform public-input schema format
  • No deterministic way to fetch verification keys
  • Each project reinvents metadata formats and tooling
  • Indexers and explorers lack a clean update signal

ZKMeta addresses these gaps without constraining proving systems or proof structures.

Specification Summary

The core interface:

interface IZKMetadata {
    event CircuitMetadataUpdated(bytes32 circuitId, uint64 circuitVersion, bytes4 proofSystem);

    function circuitId() external view returns (bytes32);
    function circuitVersion() external view returns (uint64);
    function publicInputsSchemaHash() external view returns (bytes32);
    function publicInputsSchemaURI() external view returns (string memory);
    function verificationKeyURI() external view returns (string memory);
    function proofSystem() external view returns (bytes4);
}
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