signHash method

SteemSignature signHash(Uint8List sha256Data)

Sign the SHA256 hashed data using the private key

Implementation

SteemSignature signHash(Uint8List sha256Data) {
  if (sha256Data.lengthInBytes != 32 || sha256Data.isEmpty) {
    throw ('buf_sha256: 32 byte buffer requred');
  }
  var nonce = 0;
  var n = SteemKey.secp256k1.n;
  var e = decodeBigInt(sha256Data);

  while (true) {
    _deterministicGenerateK(sha256Data, d!, e, nonce++);
    var N_OVER_TWO = n >> 1;
    if (_s.compareTo(N_OVER_TWO) > 0) {
      _s = n - _s;
    }
    var sig = ECSignature(_r, _s);

    var der = SteemSignature.ecSigToDER(sig);

    var lenR = der.elementAt(3);
    var lenS = der.elementAt(5 + lenR);
    if (lenR == 32 && lenS == 32) {
      var i = SteemSignature.calcPubKeyRecoveryParam(
          decodeBigInt(sha256Data), sig, toPublicKey());
      i += 4; // compressed
      i += 27; // compact  //  24 or 27 :( forcing odd-y 2nd key candidate)
      return SteemSignature(i, sig.r, sig.s);
    }
    if (nonce % 10 == 0) {
      print('WARN: $nonce attempts to find canonical signature');
    }
  }
}