verify function

bool verify(Uint8List hash, Uint8List q, Uint8List signature)

Verify Signature

Implementation

bool verify(Uint8List hash, Uint8List q, Uint8List signature) {
  if (!isScalar(hash)) throw ArgumentError(_throwBadHash);
  if (!isPoint(q)) throw ArgumentError(_throwBadPoint);
  // 1.4.1 Enforce r and s are both integers in the interval [1, n − 1] (1, isSignature enforces '< n - 1')
  if (!isSignature(signature)) throw ArgumentError(_throwBadSignature);

  ECPoint? Q = decodeFrom(q);
  BigInt r = fromBuffer(signature.sublist(0, 32));
  BigInt s = fromBuffer(signature.sublist(32, 64));

  final signer = ECDSASigner(null, HMac(SHA256Digest(), 64));
  signer.init(false, PublicKeyParameter(ECPublicKey(Q, _secp256k1)));
  return signer.verifySignature(hash, ECSignature(r, s));
  /* STEP BY STEP
  // 1.4.1 Enforce r and s are both integers in the interval [1, n − 1] (2, enforces '> 0')
  if (r.compareTo(n) >= 0) return false;
  if (s.compareTo(n) >= 0) return false;

  // 1.4.2 H = Hash(M), already done by the user
  // 1.4.3 e = H
  BigInt e = fromBuffer(hash);

  BigInt sInv = s.modInverse(n);
  BigInt u1 = (e * sInv) % n;
  BigInt u2 = (r * sInv) % n;

  // 1.4.5 Compute R = (xR, yR)
  //               R = u1G + u2Q
  ECPoint R = G * u1 + Q * u2;

  // 1.4.5 (cont.) Enforce R is not at infinity
  if (R.isInfinity) return false;

  // 1.4.6 Convert the field element R.x to an integer
  BigInt xR = R.x.toBigInteger();

  // 1.4.7 Set v = xR mod n
  BigInt v = xR % n;

  // 1.4.8 If v = r, output "valid", and if v != r, output "invalid"
  return v.compareTo(r) == 0;
  */
}