public bool VerifySignature(string message, Point signature, CurvePoint publicKey)
{
var hash = BigIntegerExtensions.ComputeSHA1(message);
// Console.WriteLine($"Hash of {message} is {hash}");
var w = signature.YCoordinate.FindModularInverse(Order);
/// Console.WriteLine($"W: {w}");
if (w.HasValue)
{
var u1 = Multiply(
BigInteger.Remainder(
BigInteger.Multiply(
hash,
w.Value),
Order));
var u2 = publicKey.Multiply(
BigInteger.Remainder(
BigInteger.Multiply(
signature.XCoordinate,
w.Value),
publicKey.Order));
// Console.WriteLine($"u1: {u1}, u2: {u2}");
var check = Curve.CalculateAddition(u1.Point, u2.Point);
var ret = BigInteger.Equals(check.XCoordinate, signature.XCoordinate);
// Console.WriteLine($"Checkpoint {check} X == signature {signature} X: {ret}");
return(ret);
}
else
{
throw new InvalidOperationException($"Multiplicative modular inverse of {signature.YCoordinate} cannot be calculated on mod {Order}");
}
}
public static BigInteger ToSecret(this CurvePoint point)
{
return(BigInteger.Remainder(BigInteger.Multiply(point.Point.XCoordinate, point.Point.YCoordinate), point.Curve.Modulo));
}
public CurvePoint(CurvePoint generation, BigInteger multiplier)
{
Curve = generation.Curve;
Order = generation.Order;
Point = Curve.CalculateMultiplication(generation.Point, multiplier);
}
