PublicKey RecoverPublicKey(byte[] bufferSha256)
{
var e = BigInteger.FromBuffer(bufferSha256);
var q = ECDSA.RecoverPublicKey(Curve.SecP256k1, e, new ECSignature(r, s), ( byte )((i - 27) & 3));
return(PublicKey.FromPoint(q));
}
static Signature SignBufferSha256(byte[] bufferSha256, PrivateKey privateKey)
{
if (bufferSha256.Length != 32)
{
throw new ArgumentException("bufferSha256: 32 byte buffer requred");
}
var nonce = uint.MinValue;
var e = BigInteger.FromBuffer(bufferSha256);
ECSignature ecSignature = null;
var i = byte.MinValue;
while (true)
{
ecSignature = ECDSA.Sign(Curve.SecP256k1, bufferSha256, privateKey.D, nonce++);
var der = ecSignature.ToDER();
var lengthR = der[3];
var lengthS = der[5 + lengthR];
if (lengthR == 32 && lengthS == 32)
{
i = ECDSA.CalculatePublicKeyRecoveryParameter(Curve.SecP256k1, e, ecSignature, privateKey.ToPublicKey().Q);
i += 4; // compressed
i += 27; // compact // 24 or 27 :( forcing odd-y 2nd key candidate)
break;
}
if (nonce % 10 == 0)
{
Unity.Console.Warning(nonce, "attempts to find canonical signature");
}
}
return(new Signature(ecSignature.R, ecSignature.S, i));
}
bool VerifyHash(byte[] hash, PublicKey publicKey)
{
if (hash.Length != 32)
{
Unity.Console.DebugWarning("A sha256 hash should be 32 bytes long, instead got ", hash.Length);
}
return(ECDSA.Verify(Curve.SecP256k1, hash, new ECSignature(r, s), publicKey.Q));
}
