//Implementation of https://blog.todotnet.com/2018/02/public-private-keys-and-signing/
public static string GetSignature(string privateKey, string message)
{
Org.BouncyCastle.Asn1.X9.X9ECParameters curve = SecNamedCurves.GetByName("secp256k1");
ECDomainParameters domain = new ECDomainParameters(curve.Curve, curve.G, curve.N, curve.H);
ECPrivateKeyParameters keyParameters = new ECPrivateKeyParameters(new Org.BouncyCastle.Math.BigInteger(privateKey), domain);
ISigner signer = SignerUtilities.GetSigner("SHA-256withECDSA");
signer.Init(true, keyParameters);
signer.BlockUpdate(Encoding.ASCII.GetBytes(message), 0, message.Length);
byte[] signature = signer.GenerateSignature();
return(Base58Encoding.Encode(signature));
}
public static bool VerifySignature(string message, string publicKey, string signature)
{
var curve = SecNamedCurves.GetByName("secp256k1");
var domain = new ECDomainParameters(curve.Curve, curve.G, curve.N, curve.H);
var publicKeyBytes = Base58Encoding.Decode(publicKey);
var q = curve.Curve.DecodePoint(publicKeyBytes);
var keyParameters = new ECPublicKeyParameters(q, domain);
ISigner signer = SignerUtilities.GetSigner("SHA-256withECDSA");
signer.Init(false, keyParameters);
signer.BlockUpdate(Encoding.ASCII.GetBytes(message), 0, message.Length);
var signatureBytes = Base58Encoding.Decode(signature);
return(signer.VerifySignature(signatureBytes));
}