private static EllipticCurve SetupCurve(IConfigurationRoot config)
{
var curveSection = config.GetSection("EllipticCurve");
if (curveSection is null)
{
return(new EllipticCurve());
}
System.Globalization.NumberStyles ns;
if (config["NumberStyle"] == "dec")
{
ns = System.Globalization.NumberStyles.Integer;
}
else
{
ns = System.Globalization.NumberStyles.HexNumber;
}
var a = BigInteger.Parse(curveSection["A"], ns);
var b = BigInteger.Parse(curveSection["B"], ns);
var p = BigInteger.Parse(curveSection["P"], ns);
var n = BigInteger.Parse(curveSection["N"], ns);
var g = new BigIntegerPoint(BigInteger.Parse(curveSection.GetSection("G")["X"], ns), BigInteger.Parse(curveSection.GetSection("G")["Y"], ns));
return(new EllipticCurve(a, b, p, g, n));
}
/// <summary>
/// Generates a random private-public key pair.
/// </summary>
/// <returns>The tuple consists of a private and public key</returns>
public (BigInteger privateKey, BigIntegerPoint publicKey) GenerateKeyPair()
{
BigInteger privateKey = EllipticCurveHelpers.RandomIntegerBelow(this.Curve.N);
BigIntegerPoint publicKey = this.Curve.ScalarMult(privateKey, this.Curve.G);
return(privateKey, publicKey);
}
/// <summary>
/// Generates signature.
/// </summary>
/// <param name="privateKey"></param>
/// <param name="message"></param>
/// <returns></returns>
public (BigInteger r, BigInteger s) Sign(string message, BigInteger privateKey)
{
BigInteger z = this.HashMessage(message);
BigInteger r = 0;
BigInteger s = 0;
while (r == 0 || s == 0)
{
BigInteger k = EllipticCurveHelpers.RandomIntegerBelow(this.Curve.N);
BigIntegerPoint point = this.Curve.ScalarMult(k, this.Curve.G);
r = EllipticCurveHelpers.MathMod(point.X, this.Curve.N);
s = EllipticCurveHelpers.MathMod((z + r * privateKey) * this.Curve.InverseMod(k, this.Curve.N), this.Curve.N);
}
return(r, s);
}
public static ECPoint GetSharedKey(this DiffieHellman dh, byte[] bytePrivateKey, ECPoint bytePublicKey)
{
var privateKey = new BigInteger(bytePrivateKey);
var publicKey = new BigIntegerPoint
{
X = new BigInteger(bytePublicKey.X),
Y = new BigInteger(bytePublicKey.Y),
};
var sharedKey = dh.GetSharedkey(privateKey, publicKey);
var result = new ECPoint
{
X = sharedKey.X.ToByteArray(),
Y = sharedKey.Y.ToByteArray(),
};
return(result);
}
