verify function

bool verify(List<int> msg, BigInt? sigR, BigInt? sigS, List<int> key,)

Implementation

bool verify(List<int> msg, BigInt? sigR, BigInt? sigS, List<int> key) {
  bool isZero(BigInt test) =>
      test.compareTo(BigInt.from(0)) != 0 ? false : true;
  bool isGteCurve(BigInt test) => test.compareTo(params.n) > 1 ? true : false;

  var sig = new SchnorrSignature(sigR, sigS);

  if (isZero(sig.s!) || isZero(sig.r!)) {
    throw 'Invalid signature';
  }

  if (sig.s!.isNegative || sig.r!.isNegative) {
    throw 'Invalid signature';
  }

  if (isGteCurve(sig.s!) || isGteCurve(sig.r!)) {
    throw 'Invalid signature';
  }

  ECPoint kpub = params.curve.decodePoint(key)!;

  ///
  ///   if (!curve.validate(kpub)) {
  ///     throw new Error('Invalid public key')
  ///   }
  ///

  ECPoint l = (kpub * (sig.r))!;

  ECPoint? r = params.G * (sig.s);

  ECPoint Q = (l + r)!;

  if (Q.isInfinity) {
    throw 'Invalid intermediate point.';
  }

  BigInt compressedQ = numbers.bytesToInt(Q.getEncoded());

  BigInt r1 = hash(compressedQ, key, msg) % (params.n);

  if (isZero(r1)) {
    throw 'Invalid hash.';
  }

  return r1 == sig.r;
}