public static string GetPublicKeyFromPrivateKey(string privateKey)
{
byte[] privateKeyBytes = HexStringToByteArray(privateKey);
Org.BouncyCastle.Math.EC.ECPoint q = domainParameters.G.Multiply(new BigInteger(privateKeyBytes));
return(ToHexString(q.GetEncoded()));
}
protected string EncodeECPointHexCompressed(Org.BouncyCastle.Math.EC.ECPoint point)
{
var compressedPoint = point.GetEncoded(true);
BigInteger biInt = new BigInteger(compressedPoint);
return(biInt.ToString(16));
}
/// <summary>
/// Creates the challenge for the Chaum-Pedersen protocol, using the strong Fiat-Shamir transformation.
/// Hashes all input and a fixed domain to create an unpredictable number. Used by the initiator and token service.
/// </summary>
/// <param name="G">Curve generator</param>
/// <param name="P">Randomised point on curve</param>
/// <param name="K">Public key K = k*G</param>
/// <param name="Q">Signature Q = k*P</param>
/// <param name="X">Commitment X = r*G</param>
/// <param name="Y">Commitment Y = r*P</param>
/// <returns>A random number uniquely based on all inputs</returns>
public static BigInteger CreateChallenge(ECPoint G, ECPoint P, ECPoint K, ECPoint Q, ECPoint X, ECPoint Y)
{
// Encode the ECPoint inputs
byte[]? GEncoded = G.GetEncoded();
byte[]? PEncoded = P.GetEncoded();
byte[]? KEncoded = K.GetEncoded();
byte[]? QEncoded = Q.GetEncoded();
byte[]? XEncoded = X.GetEncoded();
byte[]? YEncoded = Y.GetEncoded();
// Domain separation: make sure hash is independent of other systems
string?domain = "AnonymousTokens";
byte[]? domainEncoded = Encoding.ASCII.GetBytes(domain);
// Using concat() is best for performance: https://stackoverflow.com/a/415396
IEnumerable <byte> points = domainEncoded
.Concat(GEncoded)
.Concat(PEncoded)
.Concat(KEncoded)
.Concat(QEncoded)
.Concat(XEncoded)
.Concat(YEncoded);
SHA256? sha256 = SHA256.Create();
BigInteger?hashAsInt = new BigInteger(sha256.ComputeHash(points.ToArray()));
return(hashAsInt.Mod(G.Curve.Order));
}
/// <summary>
/// Gets the public key from the private key.
/// </summary>
/// <param name="privateKey"></param>
/// <returns></returns>
public static string GetPublicKey(string privateKey)
{
BigInteger privateKeyInt = new BigInteger(privateKey, 16);
X9ECParameters curve = SecNamedCurves.GetByName("secp256k1");
ECDomainParameters domain = new ECDomainParameters(curve.Curve, curve.G, curve.N, curve.H);
ECPoint q = domain.G.Multiply(privateKeyInt);
byte[] bytes = q.GetEncoded();
return(Hex.ToHexString(bytes));
}
public override byte[] GetCanoncialBytes()
{
return(publicKey.GetEncoded(true));
}
