@anoncitizen/contracts

Solidity smart contracts for on-chain AnonCitizen ZK proof verification.

Installation

npm install @anoncitizen/contracts

Contracts

AnonCitizen.sol

Wrapper contract providing:

• Groth16 proof verification via verifyAndRecord()
• Nullifier tracking to prevent replay attacks
• Trusted public key hash registry for UIDAI key rotation
• ProofVerified event emission for indexing

Groth16Verifier.sol

Auto-generated Groth16 pairing verifier (from snarkjs). Uses BN254 elliptic curve precompiles.

IAnonCitizen.sol

Interface for the AnonCitizen contract.

Usage

Deploy

npx hardhat run scripts/deploy.ts --network sepolia

Integrate

IAnonCitizen anoncitizen = IAnonCitizen(deployedAddress);

// Verify and record a proof (reverts on failure)
anoncitizen.verifyAndRecord(pA, pB, pC, pubSignals);

// Check if a nullifier was already used
bool used = anoncitizen.isNullifierUsed(nullifier);

Public Signals

[0] nullifier      — unique per (identity, nullifierSeed)
[1] timestamp      — UNIX UTC from Aadhaar document
[2] pubKeyHash     — hash of UIDAI RSA public key
[3] signalHash     — hash of bound signal (anti-frontrun)
[4] nullifierSeed  — application-provided scope seed
[5] ageAbove18     — 1 if age >= 18, 0 if not revealed
[6] gender         — 1=M, 2=F, 3=T, 0 if not revealed
[7] state          — encoded state, 0 if not revealed
[8] pincode        — 6-digit PIN, 0 if not revealed

Development

npx hardhat compile
npx hardhat test
REPORT_GAS=true npx hardhat test  # with gas benchmarks

License

MIT