public override ECPoint TwicePlus(ECPoint b)
{
if (this.IsInfinity)
return b;
if (b.IsInfinity)
return Twice();
ECCurve curve = this.Curve;
ECFieldElement X1 = this.RawXCoord;
if (X1.IsZero)
{
// A point with X == 0 is it's own additive inverse
return b;
}
int coord = curve.CoordinateSystem;
switch (coord)
{
case ECCurve.COORD_LAMBDA_PROJECTIVE:
{
// NOTE: twicePlus() only optimized for lambda-affine argument
ECFieldElement X2 = b.RawXCoord, Z2 = b.RawZCoords[0];
if (X2.IsZero || !Z2.IsOne)
{
return Twice().Add(b);
}
ECFieldElement L1 = this.RawYCoord, Z1 = this.RawZCoords[0];
ECFieldElement L2 = b.RawYCoord;
ECFieldElement X1Sq = X1.Square();
ECFieldElement L1Sq = L1.Square();
ECFieldElement Z1Sq = Z1.Square();
ECFieldElement L1Z1 = L1.Multiply(Z1);
ECFieldElement T = curve.A.Multiply(Z1Sq).Add(L1Sq).Add(L1Z1);
ECFieldElement L2plus1 = L2.AddOne();
ECFieldElement A = curve.A.Add(L2plus1).Multiply(Z1Sq).Add(L1Sq).MultiplyPlusProduct(T, X1Sq, Z1Sq);
ECFieldElement X2Z1Sq = X2.Multiply(Z1Sq);
ECFieldElement B = X2Z1Sq.Add(T).Square();
if (B.IsZero)
{
if (A.IsZero)
{
return b.Twice();
}
return curve.Infinity;
}
if (A.IsZero)
{
return new F2mPoint(curve, A, curve.B.Sqrt(), IsCompressed);
}
ECFieldElement X3 = A.Square().Multiply(X2Z1Sq);
ECFieldElement Z3 = A.Multiply(B).Multiply(Z1Sq);
ECFieldElement L3 = A.Add(B).Square().MultiplyPlusProduct(T, L2plus1, Z3);
return new F2mPoint(curve, X3, L3, new ECFieldElement[] { Z3 }, IsCompressed);
}
default:
{
return Twice().Add(b);
}
}
}
/**
* Tests <code>ECPoint.add()</code> and <code>ECPoint.subtract()</code>
* for the given point and the given point at infinity.
*
* @param p
* The point on which the tests are performed.
* @param infinity
* The point at infinity on the same curve as <code>p</code>.
*/
private void ImplTestAddSubtract(ECPoint p, ECPoint infinity)
{
AssertPointsEqual("Twice and Add inconsistent", p.Twice(), p.Add(p));
AssertPointsEqual("Twice p - p is not p", p, p.Twice().Subtract(p));
AssertPointsEqual("TwicePlus(p, -p) is not p", p, p.TwicePlus(p.Negate()));
AssertPointsEqual("p - p is not infinity", infinity, p.Subtract(p));
AssertPointsEqual("p plus infinity is not p", p, p.Add(infinity));
AssertPointsEqual("infinity plus p is not p", p, infinity.Add(p));
AssertPointsEqual("infinity plus infinity is not infinity ", infinity, infinity.Add(infinity));
AssertPointsEqual("Twice infinity is not infinity ", infinity, infinity.Twice());
}
/**
* Simple shift-and-add multiplication. Serves as reference implementation
* to verify (possibly faster) implementations in
* {@link org.bouncycastle.math.ec.ECPoint ECPoint}.
*
* @param p
* The point to multiply.
* @param k
* The multiplier.
* @return The result of the point multiplication <code>kP</code>.
*/
private ECPoint Multiply(ECPoint p, BigInteger k)
{
ECPoint q = p.Curve.Infinity;
int t = k.BitLength;
for (int i = 0; i < t; i++)
{
if (i != 0)
{
p = p.Twice();
}
if (k.TestBit(i))
{
q = q.Add(p);
}
}
return q;
}
/**
* Tests <code>ECPoint.add()</code> and <code>ECPoint.subtract()</code>
* for the given point and the given point at infinity.
*
* @param p
* The point on which the tests are performed.
* @param infinity
* The point at infinity on the same curve as <code>p</code>.
*/
private void implTestAddSubtract(ECPoint p, ECPoint infinity)
{
Assert.AreEqual(p.Twice(), p.Add(p), "Twice and Add inconsistent");
Assert.AreEqual(p, p.Twice().Subtract(p), "Twice p - p is not p");
Assert.AreEqual(infinity, p.Subtract(p), "p - p is not infinity");
Assert.AreEqual(p, p.Add(infinity), "p plus infinity is not p");
Assert.AreEqual(p, infinity.Add(p), "infinity plus p is not p");
Assert.AreEqual(infinity, infinity.Add(infinity), "infinity plus infinity is not infinity ");
}
/**
* Simple shift-and-add multiplication. Serves as reference implementation
* to verify (possibly faster) implementations, and for very small scalars.
*
* @param p
* The point to multiply.
* @param k
* The multiplier.
* @return The result of the point multiplication <code>kP</code>.
*/
public static ECPoint ReferenceMultiply(ECPoint p, BigInteger k)
{
BigInteger x = k.Abs();
ECPoint q = p.Curve.Infinity;
int t = x.BitLength;
if (t > 0)
{
if (x.TestBit(0))
{
q = p;
}
for (int i = 1; i < t; i++)
{
p = p.Twice();
if (x.TestBit(i))
{
q = q.Add(p);
}
}
}
return k.SignValue < 0 ? q.Negate() : q;
}
public override ECPoint TwicePlus(ECPoint b)
{
if (base.IsInfinity)
{
return(b);
}
if (b.IsInfinity)
{
return(this.Twice());
}
ECCurve curve = this.Curve;
ECFieldElement rawXCoord = base.RawXCoord;
if (rawXCoord.IsZero)
{
return(b);
}
int coordinateSystem = curve.CoordinateSystem;
int num = coordinateSystem;
if (num != 6)
{
return(this.Twice().Add(b));
}
ECFieldElement rawXCoord2 = b.RawXCoord;
ECFieldElement eCFieldElement = b.RawZCoords[0];
if (rawXCoord2.IsZero || !eCFieldElement.IsOne)
{
return(this.Twice().Add(b));
}
ECFieldElement rawYCoord = base.RawYCoord;
ECFieldElement eCFieldElement2 = base.RawZCoords[0];
ECFieldElement rawYCoord2 = b.RawYCoord;
ECFieldElement x = rawXCoord.Square();
ECFieldElement b2 = rawYCoord.Square();
ECFieldElement eCFieldElement3 = eCFieldElement2.Square();
ECFieldElement b3 = rawYCoord.Multiply(eCFieldElement2);
ECFieldElement b4 = curve.A.Multiply(eCFieldElement3).Add(b2).Add(b3);
ECFieldElement eCFieldElement4 = rawYCoord2.AddOne();
ECFieldElement eCFieldElement5 = curve.A.Add(eCFieldElement4).Multiply(eCFieldElement3).Add(b2).MultiplyPlusProduct(b4, x, eCFieldElement3);
ECFieldElement eCFieldElement6 = rawXCoord2.Multiply(eCFieldElement3);
ECFieldElement eCFieldElement7 = eCFieldElement6.Add(b4).Square();
if (eCFieldElement7.IsZero)
{
if (eCFieldElement5.IsZero)
{
return(b.Twice());
}
return(curve.Infinity);
}
else
{
if (eCFieldElement5.IsZero)
{
return(new F2mPoint(curve, eCFieldElement5, curve.B.Sqrt(), base.IsCompressed));
}
ECFieldElement x2 = eCFieldElement5.Square().Multiply(eCFieldElement6);
ECFieldElement eCFieldElement8 = eCFieldElement5.Multiply(eCFieldElement7).Multiply(eCFieldElement3);
ECFieldElement y = eCFieldElement5.Add(eCFieldElement7).Square().MultiplyPlusProduct(b4, eCFieldElement4, eCFieldElement8);
return(new F2mPoint(curve, x2, y, new ECFieldElement[]
{
eCFieldElement8
}, base.IsCompressed));
}
}
