verify function

bool verify(PublicKey publicKey, Uint8List message, Uint8List sig)

Verify reports whether sig is a valid signature of message by publicKey. It will throw ArgumentError if publicKey.bytes.length is not PublicKeySize.

Implementation

bool verify(PublicKey publicKey, Uint8List message, Uint8List sig) {
  if (publicKey.bytes.length != PublicKeySize) {
    throw ArgumentError(
        'ed25519: bad publicKey length ${publicKey.bytes.length}');
  }
  if (sig.length != SignatureSize || sig[63] & 224 != 0) {
    return false;
  }

  var A = ExtendedGroupElement();
  var publicKeyBytes = Uint8List.fromList(publicKey.bytes);
  if (!A.FromBytes(publicKeyBytes)) {
    return false;
  }
  FeNeg(A.X, A.X);
  FeNeg(A.T, A.T);

  var output = AccumulatorSink<Digest>();
  var input = sha512.startChunkedConversion(output);
  input.add(sig.sublist(0, 32));
  input.add(publicKeyBytes);
  input.add(message);
  input.close();
  var digest = output.events.single.bytes;

  var hReduced = Uint8List(32);
  ScReduce(hReduced, digest as Uint8List);

  var R = ProjectiveGroupElement();
  var s = sig.sublist(32);

  if (!ScMinimal(s)) {
    return false;
  }

  GeDoubleScalarMultVartime(R, hReduced, A, s);

  var checkR = Uint8List(32);
  R.ToBytes(checkR);
  return ListEquality().equals(sig.sublist(0, 32), checkR);
}