org.bouncycastle.math.ec.custom.sec.SecT193R2Point Maven / Gradle / Ivy

Go to download
Show more of this group Show more artifacts with this name
Show all versions of bcprov-ext-debug-jdk18on Show documentation
The Bouncy Castle Crypto package is a Java implementation of cryptographic algorithms. This jar contains JCE provider and lightweight API for the Bouncy Castle Cryptography APIs for Java 1.8 and later with debug enabled.
The newest version!
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 SecT193R2Point extends AbstractF2m
{
    SecT193R2Point(ECCurve curve, ECFieldElement x, ECFieldElement y)
    {
        super(curve, x, y);
    }

    SecT193R2Point(ECCurve curve, ECFieldElement x, ECFieldElement y, ECFieldElement[] zs)
    {
        super(curve, x, y, zs);
    }

    protected ECPoint detach()
    {
        return new SecT193R2Point(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).add(curve.getA());
            if (X3.isZero())
            {
                return new SecT193R2Point(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 SecT193R2Point(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 SecT193R2Point(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 a = curve.getA();
        ECFieldElement aZ1Sq = Z1IsOne ? a : a.multiply(Z1Sq);
        ECFieldElement T = L1.square().add(L1Z1).add(aZ1Sq);
        if (T.isZero())
        {
            return new SecT193R2Point(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 SecT193R2Point(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 = curve.getA().multiply(Z1Sq).add(L1Sq).add(L1Z1);
        ECFieldElement L2plus1 = L2.addOne();
        ECFieldElement A = curve.getA().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.getInfinity();
        }

        if (A.isZero())
        {
            return new SecT193R2Point(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, L2plus1, Z3);

        return new SecT193R2Point(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 SecT193R2Point(curve, X, L.add(Z), new ECFieldElement[]{ Z });
    }
}