sign method

Implementation

List<int> sign(List<int> data, HashFunc hashMethod) {
  final order = generator.order;
  if (order == null) {
    throw ArgumentException.invalidOperationArguments(
      "sign",
      reason: "Invalid curve generator.",
    );
  }
  List<int> dom = List.empty();
  if (generator.curve == Curves.curveEd448) {
    dom = [...'SigEd448'.codeUnits, 0x00, 0x00];
  }
  final r = BigintUtils.fromBytes(
    hashMethod().update([...dom, ...extendedKey, ...data]).digest(),
    byteOrder: Endian.little,
  );
  final R = (generator * r).toBytes();
  BigInt k = BigintUtils.fromBytes(
    hashMethod().update([
      ...dom,
      ...R,
      ...publicKey.toBytes(),
      ...data,
    ]).digest(),
    byteOrder: Endian.little,
  );

  k %= order;
  final s = (r + k * secret) % order;
  final signature = [
    ...R,
    ...BigintUtils.toBytes(s, length: baselen, order: Endian.little),
  ];
  if (publicKey.verify(data, signature, hashMethod)) {
    return signature;
  }
  throw CryptoSignException.signatureVerificationFailed;
}