ZK Contracts

This page documents the on-chain contracts for ZK-based decisions and how to submit proofs on Base.

Status

Contracts are deployed on Base mainnet (8453).

Contracts

• Verifier.sol
• DecisionRegistry.sol

Base Mainnet (8453)

• Verifier: 0x708FB78d97b32250e302F33A1A81936C8B618625
• DecisionRegistry (Proxy): 0x694A54Bf1b7659e8A7e63CD8a45de378458659D8

Resubmission

The DecisionRegistry allows resubmission — calling submitDecision for the same subject + context will overwrite the existing record with the updated decision and proof.

ABI & Types

TypeScript ABI modules live in packages/contracts/abi. Inside other packages you can import them via the workspace alias:

import { VERIFIER_ABI, DECISION_REGISTRY_ABI } from "@basecred/contracts/abi";

Each export includes a readonly tuple plus a typed alias (Groth16VerifierAbi, DecisionRegistryAbi).

DecisionRegistry Interface

Function signature:

function submitDecision(
    bytes32 subjectHash,
    bytes32 context,
    uint8 decision,
    bytes32 policyHash,
    uint256[2] a,
    uint256[2][2] b,
    uint256[2] c,
    uint256[3] publicSignals
) external

Event:

event DecisionSubmitted(
    bytes32 indexed subjectHash,
    bytes32 indexed context,
    uint8 decision,
    bytes32 policyHash,
    uint64 timestamp
);

Public Signals

• publicSignals[0] must equal policyHash.
• publicSignals[1] must equal contextId (numeric context selector).
• publicSignals[2] must equal decision (numeric decision encoding).

Context IDs

• 0 -> allowlist.general
• 1 -> comment
• 2 -> publish
• 3 -> apply
• 4 -> governance.vote

Example Transaction Payload

{
  "subjectHash": "0x<bytes32>",
  "context": "0x<bytes32(contextId)>",
  "decision": 1,
  "policyHash": "0x<bytes32>",
  "a": ["0x...", "0x..."],
  "b": [["0x...", "0x..."], ["0x...", "0x..."]],
  "c": ["0x...", "0x..."],
  "publicSignals": ["0x<policyHash>", "0x<contextId>", "0x<decision>"]
}

Notes

• Replace the placeholder Verifier.sol with the Groth16 verifier generated by snarkjs.
• Ensure the circuit’s public signal layout matches publicSignals ordering above.
• context must be encoded as bytes32(uint256(contextId)) when submitting on-chain.
• policyHash must be reduced into the BN254 field (value < r).

Generate Verifier (snarkjs)

snarkjs zkey export solidityverifier circuit_final.zkey Verifier.sol