Zero-knowledge proofs

template AgeCheck() {
    // Private inputs
    signal input birthYear;
    signal input birthMonth;
    signal input birthDay;
    signal input dobHash;
    signal input userSalt;

    // Public inputs
    signal input ageThreshold;
    signal input referenceDate;
    signal input identityCommitment;
    signal input intentHash;
    
    // ... constraints ...
}

component main {public [ageThreshold, referenceDate, identityCommitment, intentHash]} = AgeCheck();

template PoolSpend(depth) {
    // Private inputs
    signal input noteAmount;
    signal input ownerKey;
    signal input salt;
    signal input pathElements[depth];
    signal input pathIndices[depth];

    // Public inputs
    signal input merkleRoot;
    signal input nullifier;
    signal input recipient;
    signal input withdrawAmount;
    signal input changeCommitment;
    
    // ... constraints ...
}

component main {public [merkleRoot, nullifier, recipient, withdrawAmount, changeCommitment]} = PoolSpend(20);

template MerkleProof(depth) {
    signal input leaf;
    signal input pathElements[depth];
    signal input pathIndices[depth]; // 0 = left, 1 = right

    signal output root;

    component hashers[depth];
    component indexChecks[depth];

    signal currentHash[depth + 1];
    currentHash[0] <== leaf;

    for (var i = 0; i < depth; i++) {
        // Ensure pathIndices[i] is binary (0 or 1)
        indexChecks[i] = IsZero();
        indexChecks[i].in <== pathIndices[i] * (pathIndices[i] - 1);
        indexChecks[i].out === 1;

        hashers[i] = Poseidon(2);

        // Compute hash based on whether current node is left or right
        // ...

        currentHash[i + 1] <== hashers[i].out;
    }

    root <== currentHash[depth];
}

/// Create and share a new verification key for a circuit.
/// Called once during deployment to register each circuit's verification key.
public fun create_verification_key(
    circuit_name: std::string::String,
    raw_vk: vector<u8>,
    ctx: &mut TxContext,
) {
    let curve = groth16::bn254();
    let pvk = groth16::prepare_verifying_key(&curve, &raw_vk);

    let vk = VerificationKey {
        id: object::new(ctx),
        circuit_name,
        pvk,
    };

    transfer::share_object(vk);
}

/// Verify a Groth16 proof against the stored verification key.
/// Returns true if valid, false otherwise.
public(package) fun verify_proof(
    vk: &VerificationKey,
    proof_bytes: &vector<u8>,
    public_inputs_bytes: &vector<u8>,
): bool {
    assert!(!proof_bytes.is_empty(), EEmptyProof);
    assert!(!public_inputs_bytes.is_empty(), EEmptyPublicInputs);

    let curve = groth16::bn254();
    let proof_points = groth16::proof_points_from_bytes(*proof_bytes);
    let public_inputs = groth16::public_proof_inputs_from_bytes(*public_inputs_bytes);

    groth16::verify_groth16_proof(&curve, &vk.pvk, &public_inputs, &proof_points)
}

// 1. Verify ZK proof of buyer eligibility
zk_verifier::assert_proof_valid(zk_vk, &zk_proof, &zk_public_inputs);

// 2. Verify intent signature (buyer signed the canonical intent hash)
intent::verify_intent_signature(&intent_sig, &intent_hash, &buyer_pubkey);

// 3. Split exact amount and transfer to merchant
let exact = coin::split(payment, amount, ctx);
transfer::public_transfer(exact, merchant);