public ECPoint Subtract(ECPoint b)
{
return Add(b.Negate());
}
public ECPoint Add(ECPoint b)
{
BigInteger m;
BigInteger r = 0;
if (this.IsInfinity)
{
return b;
}
if (b.IsInfinity)
{
return this;
}
if (X - b.X == 0)
{
if (Y - b.Y == 0)
{
m = 3 * X * X * (2 * Y).ModInverse(Secp256k1.P);
}
else
{
return ECPoint.Infinity;
}
}
else
{
var mx = (X - b.X);
if (mx < 0)
{
mx += Secp256k1.P;
}
m = (Y - b.Y) * mx.ModInverse(Secp256k1.P);
}
m = m % Secp256k1.P;
var v = Y - m * X;
var x3 = (m * m - X - b.X);
x3 = x3 % Secp256k1.P;
if (x3 < 0)
{
x3 += Secp256k1.P;
}
var y3 = -(m * x3 + v);
y3 = y3 % Secp256k1.P;
if (y3 < 0)
{
y3 += Secp256k1.P;
}
return new ECPoint(x3, y3);
}