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org.bouncycastle.math.ec.custom.sec.SecT163R2Point Maven / Gradle / Ivy
package org.bouncycastle.math.ec.custom.sec;
import org.bouncycastle.math.ec.ECConstants;
import org.bouncycastle.math.ec.ECCurve;
import org.bouncycastle.math.ec.ECFieldElement;
import org.bouncycastle.math.ec.ECPoint;
import org.bouncycastle.math.ec.ECPoint.AbstractF2m;
public class SecT163R2Point extends AbstractF2m
{
SecT163R2Point(ECCurve curve, ECFieldElement x, ECFieldElement y)
{
super(curve, x, y);
}
SecT163R2Point(ECCurve curve, ECFieldElement x, ECFieldElement y, ECFieldElement[] zs)
{
super(curve, x, y, zs);
}
protected ECPoint detach()
{
return new SecT163R2Point(null, getAffineXCoord(), getAffineYCoord());
}
public ECFieldElement getYCoord()
{
ECFieldElement X = x, L = y;
if (this.isInfinity() || X.isZero())
{
return L;
}
// Y is actually Lambda (X + Y/X) here; convert to affine value on the fly
ECFieldElement Y = L.add(X).multiply(X);
ECFieldElement Z = zs[0];
if (!Z.isOne())
{
Y = Y.divide(Z);
}
return Y;
}
protected boolean getCompressionYTilde()
{
ECFieldElement X = this.getRawXCoord();
if (X.isZero())
{
return false;
}
ECFieldElement Y = this.getRawYCoord();
// Y is actually Lambda (X + Y/X) here
return Y.testBitZero() != X.testBitZero();
}
public ECPoint add(ECPoint b)
{
if (this.isInfinity())
{
return b;
}
if (b.isInfinity())
{
return this;
}
ECCurve curve = this.getCurve();
ECFieldElement X1 = this.x;
ECFieldElement X2 = b.getRawXCoord();
if (X1.isZero())
{
if (X2.isZero())
{
return curve.getInfinity();
}
return b.add(this);
}
ECFieldElement L1 = this.y, Z1 = this.zs[0];
ECFieldElement L2 = b.getRawYCoord(), Z2 = b.getZCoord(0);
boolean Z1IsOne = Z1.isOne();
ECFieldElement U2 = X2, S2 = L2;
if (!Z1IsOne)
{
U2 = U2.multiply(Z1);
S2 = S2.multiply(Z1);
}
boolean Z2IsOne = Z2.isOne();
ECFieldElement U1 = X1, S1 = L1;
if (!Z2IsOne)
{
U1 = U1.multiply(Z2);
S1 = S1.multiply(Z2);
}
ECFieldElement A = S1.add(S2);
ECFieldElement B = U1.add(U2);
if (B.isZero())
{
if (A.isZero())
{
return twice();
}
return curve.getInfinity();
}
ECFieldElement X3, L3, Z3;
if (X2.isZero())
{
// TODO This can probably be optimized quite a bit
ECPoint p = this.normalize();
X1 = p.getXCoord();
ECFieldElement Y1 = p.getYCoord();
ECFieldElement Y2 = L2;
ECFieldElement L = Y1.add(Y2).divide(X1);
X3 = L.square().add(L).add(X1).addOne();
if (X3.isZero())
{
return new SecT163R2Point(curve, X3, curve.getB().sqrt());
}
ECFieldElement Y3 = L.multiply(X1.add(X3)).add(X3).add(Y1);
L3 = Y3.divide(X3).add(X3);
Z3 = curve.fromBigInteger(ECConstants.ONE);
}
else
{
B = B.square();
ECFieldElement AU1 = A.multiply(U1);
ECFieldElement AU2 = A.multiply(U2);
X3 = AU1.multiply(AU2);
if (X3.isZero())
{
return new SecT163R2Point(curve, X3, curve.getB().sqrt());
}
ECFieldElement ABZ2 = A.multiply(B);
if (!Z2IsOne)
{
ABZ2 = ABZ2.multiply(Z2);
}
L3 = AU2.add(B).squarePlusProduct(ABZ2, L1.add(Z1));
Z3 = ABZ2;
if (!Z1IsOne)
{
Z3 = Z3.multiply(Z1);
}
}
return new SecT163R2Point(curve, X3, L3, new ECFieldElement[]{ Z3 });
}
public ECPoint twice()
{
if (this.isInfinity())
{
return this;
}
ECCurve curve = this.getCurve();
ECFieldElement X1 = this.x;
if (X1.isZero())
{
// A point with X == 0 is its own additive inverse
return curve.getInfinity();
}
ECFieldElement L1 = this.y, Z1 = this.zs[0];
boolean Z1IsOne = Z1.isOne();
ECFieldElement L1Z1 = Z1IsOne ? L1 : L1.multiply(Z1);
ECFieldElement Z1Sq = Z1IsOne ? Z1 : Z1.square();
ECFieldElement T = L1.square().add(L1Z1).add(Z1Sq);
if (T.isZero())
{
return new SecT163R2Point(curve, T, curve.getB().sqrt());
}
ECFieldElement X3 = T.square();
ECFieldElement Z3 = Z1IsOne ? T : T.multiply(Z1Sq);
ECFieldElement X1Z1 = Z1IsOne ? X1 : X1.multiply(Z1);
ECFieldElement L3 = X1Z1.squarePlusProduct(T, L1Z1).add(X3).add(Z3);
return new SecT163R2Point(curve, X3, L3, new ECFieldElement[]{ Z3 });
}
public ECPoint twicePlus(ECPoint b)
{
if (this.isInfinity())
{
return b;
}
if (b.isInfinity())
{
return twice();
}
ECCurve curve = this.getCurve();
ECFieldElement X1 = this.x;
if (X1.isZero())
{
// A point with X == 0 is its own additive inverse
return b;
}
ECFieldElement X2 = b.getRawXCoord(), Z2 = b.getZCoord(0);
if (X2.isZero() || !Z2.isOne())
{
return twice().add(b);
}
ECFieldElement L1 = this.y, Z1 = this.zs[0];
ECFieldElement L2 = b.getRawYCoord();
ECFieldElement X1Sq = X1.square();
ECFieldElement L1Sq = L1.square();
ECFieldElement Z1Sq = Z1.square();
ECFieldElement L1Z1 = L1.multiply(Z1);
ECFieldElement T = Z1Sq.add(L1Sq).add(L1Z1);
ECFieldElement A = L2.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.getInfinity();
}
if (A.isZero())
{
return new SecT163R2Point(curve, A, curve.getB().sqrt());
}
ECFieldElement X3 = A.square().multiply(X2Z1Sq);
ECFieldElement Z3 = A.multiply(B).multiply(Z1Sq);
ECFieldElement L3 = A.add(B).square().multiplyPlusProduct(T, L2.addOne(), Z3);
return new SecT163R2Point(curve, X3, L3, new ECFieldElement[]{ Z3 });
}
public ECPoint negate()
{
if (this.isInfinity())
{
return this;
}
ECFieldElement X = this.x;
if (X.isZero())
{
return this;
}
// L is actually Lambda (X + Y/X) here
ECFieldElement L = this.y, Z = this.zs[0];
return new SecT163R2Point(curve, X, L.add(Z), new ECFieldElement[]{ Z });
}
}
