public void FromPoint(ProjectiveNielsPoint a)
{
Y_plus_X = a.Y_plus_X;
Y_minus_X = a.Y_minus_X;
Z = a.Z;
T2d = a.T2d;
}
public void ConditionalAssign(ProjectiveNielsPoint a, bool choice)
{
// if choice = 0, mask = (-0) = 0000...0000
// if choice = 1, mask = (-1) = 1111...1111
int mask = choice ? 0b1111_1111_1111_1111 : 0b0000_0000_0000_0000;
// *self ^= mask & (*self ^ *other);
FromPoint(GetPoint().BitXor(BitXor(a).BitAnd((uint)mask)));
}
public ProjectiveNielsPoint BitXor(ProjectiveNielsPoint a)
{
return(new ProjectiveNielsPoint
{
Y_plus_X = Y_plus_X.BitXor(a.Y_plus_X),
Y_minus_X = Y_minus_X.BitXor(a.Y_minus_X),
Z = Z.BitXor(a.Z),
T2d = T2d.BitXor(a.T2d),
});
}
public CompletedPoint Sub(ProjectiveNielsPoint other)
{
var Y_plus_X = Y.Add(X);
var Y_minus_X = Y.Sub(X);
var PM = Y_plus_X.Mul(other.Y_minus_X);
var MP = Y_minus_X.Mul(other.Y_plus_X);
var TT2d = T.Mul(other.T2d);
var ZZ = Z.Mul(other.Z);
var ZZ2 = ZZ.Add(ZZ);
return(new CompletedPoint
{
X = PM.Sub(MP),
Y = PM.Add(MP),
Z = ZZ2.Sub(TT2d),
T = ZZ2.Add(TT2d)
});
}