private ECFieldElement CheckSqrt(ECFieldElement z)
{
return z.Square().Equals(this) ? z : null;
}
internal virtual ECPoint Normalize(ECFieldElement zInv)
{
switch (this.CurveCoordinateSystem)
{
case ECCurve.COORD_HOMOGENEOUS:
case ECCurve.COORD_LAMBDA_PROJECTIVE:
{
return CreateScaledPoint(zInv, zInv);
}
case ECCurve.COORD_JACOBIAN:
case ECCurve.COORD_JACOBIAN_CHUDNOVSKY:
case ECCurve.COORD_JACOBIAN_MODIFIED:
{
ECFieldElement zInv2 = zInv.Square(), zInv3 = zInv2.Multiply(zInv);
return CreateScaledPoint(zInv2, zInv3);
}
default:
{
throw new InvalidOperationException("not a projective coordinate system");
}
}
}
protected virtual ECFieldElement CalculateJacobianModifiedW(ECFieldElement Z, ECFieldElement ZSquared)
{
ECFieldElement a4 = this.Curve.A;
if (a4.IsZero || Z.IsOne)
return a4;
if (ZSquared == null)
{
ZSquared = Z.Square();
}
ECFieldElement W = ZSquared.Square();
ECFieldElement a4Neg = a4.Negate();
if (a4Neg.BitLength < a4.BitLength)
{
W = W.Multiply(a4Neg).Negate();
}
else
{
W = W.Multiply(a4);
}
return W;
}
public override ECPoint ScaleX(ECFieldElement scale)
{
if (this.IsInfinity)
return this;
switch (CurveCoordinateSystem)
{
case ECCurve.COORD_LAMBDA_AFFINE:
{
// Y is actually Lambda (X + Y/X) here
ECFieldElement X = RawXCoord, L = RawYCoord;
ECFieldElement X2 = X.Multiply(scale);
ECFieldElement L2 = L.Add(X).Divide(scale).Add(X2);
return Curve.CreateRawPoint(X, L2, RawZCoords, IsCompressed);
}
case ECCurve.COORD_LAMBDA_PROJECTIVE:
{
// Y is actually Lambda (X + Y/X) here
ECFieldElement X = RawXCoord, L = RawYCoord, Z = RawZCoords[0];
// We scale the Z coordinate also, to avoid an inversion
ECFieldElement X2 = X.Multiply(scale.Square());
ECFieldElement L2 = L.Add(X).Add(X2);
ECFieldElement Z2 = Z.Multiply(scale);
return Curve.CreateRawPoint(X, L2, new ECFieldElement[] { Z2 }, IsCompressed);
}
default:
{
return base.ScaleX(scale);
}
}
}
private ECFieldElement CheckSqrt(ECFieldElement z)
{
return(z.Square().Equals(this) ? z : null);
}
