public bool VerifySignature(byte[] message, byte[] signature, byte[] pubkey)
{
if (pubkey.Length == 33 && (pubkey[0] == 0x02 || pubkey[0] == 0x03))
{
try
{
pubkey = ECPoint.DecodePoint(pubkey, ECCurve.Secp256r1).EncodePoint(false).Skip(1).ToArray();
}
catch
{
return(false);
}
}
else if (pubkey.Length == 65 && pubkey[0] == 0x04)
{
pubkey = pubkey.Skip(1).ToArray();
}
else if (pubkey.Length != 64)
{
throw new ArgumentException();
}
BigInteger x = new BigInteger(1, pubkey.Take(32).ToArray());
BigInteger y = new BigInteger(1, pubkey.Skip(32).ToArray());
X9ECParameters ecParams = NistNamedCurves.GetByName("P-256");
ECDomainParameters domainParameters = new ECDomainParameters(ecParams.Curve, ecParams.G, ecParams.N,
ecParams.H, ecParams.GetSeed());
var G = ecParams.G;
Org.BouncyCastle.Math.EC.ECCurve curve = ecParams.Curve;
Org.BouncyCastle.Math.EC.ECPoint q = curve.CreatePoint(x, y);
ECPublicKeyParameters pubkeyParam = new ECPublicKeyParameters(q, domainParameters);
var verifier = SignerUtilities.GetSigner("SHA-256withECDSA");
verifier.Init(false, pubkeyParam);
verifier.BlockUpdate(message, 0, message.Length);
// expected format is SEQUENCE {INTEGER r, INTEGER s}
var derSignature = new DerSequence(
// first 32 bytes is "r" number
new DerInteger(new BigInteger(1, signature.Take(32).ToArray())),
// last 32 bytes is "s" number
new DerInteger(new BigInteger(1, signature.Skip(32).ToArray())))
.GetDerEncoded();
///old verify method
///
/*
* const int ECDSA_PUBLIC_P256_MAGIC = 0x31534345;
* pubkey = BitConverter.GetBytes(ECDSA_PUBLIC_P256_MAGIC).Concat(BitConverter.GetBytes(32)).Concat(pubkey).ToArray();
* using (CngKey key = CngKey.Import(pubkey, CngKeyBlobFormat.EccPublicBlob))
* using (ECDsaCng ecdsa = new ECDsaCng(key))
* {
* var result = ecdsa.VerifyData(message, signature, HashAlgorithmName.SHA256);
* }
*/
///////////////////
return(verifier.VerifySignature(derSignature));
}