ecpoint.java

进行与数字证书相关开发必须的java源码

// Decompiled by Jad v1.5.7g. Copyright 2000 Pavel Kouznetsov.
// Jad home page: http://www.geocities.com/SiliconValley/Bridge/8617/jad.html
// Decompiler options: packimports(3) fieldsfirst ansi 
// Source File Name:   ECPoint.java

package jit.math.ec;

import jit.math.BigInteger;

// Referenced classes of package jit.math.ec:
//            ECFieldElement, ECCurve, ECConstants

public abstract class ECPoint
{
    public static class Fp extends ECPoint
    {

        public byte[] getEncoded()
        {
            byte PC;
            if(getY().toBigInteger().testBit(0))
                PC = 2;
            else
                PC = 3;
            byte X[] = getX().toBigInteger().toByteArray();
            byte PO[] = new byte[X.length + 1];
            PO[0] = PC;
            System.arraycopy(X, 0, PO, 1, X.length);
            return PO;
        }

        public byte[] getEncoded(boolean uncompress)
        {
            if(uncompress)
            {
                byte PC = 4;
                byte X[] = getX().toBigInteger().toByteArray();
                byte Y[] = getY().toBigInteger().toByteArray();
                int xOff = X[0] != 0 ? 0 : 1;
                int yOff = Y[0] != 0 ? 0 : 1;
                byte PO[] = new byte[(((X.length - xOff) + Y.length) - yOff) + 1];
                PO[0] = PC;
                System.arraycopy(X, xOff, PO, 1, X.length - xOff);
                System.arraycopy(Y, yOff, PO, (X.length - xOff) + 1, Y.length - yOff);
                return PO;
            } else
            {
                return getEncoded();
            }
        }

        public ECPoint add(ECPoint b)
        {
            if(getX().toBigInteger().equals(ECConstants.ZERO))
                return b;
            if(b.getX().toBigInteger().equals(ECConstants.ZERO))
            {
                return this;
            } else
            {
                ECFieldElement gamma = b.y.subtract(y).divide(b.x.subtract(x));
                ECFieldElement x3 = gamma.multiply(gamma).subtract(x).subtract(b.x);
                ECFieldElement y3 = gamma.multiply(x.subtract(x3)).subtract(y);
                return new Fp(curve, x3, y3);
            }
        }

        public ECPoint twice()
        {
            if(getX().toBigInteger().equals(ECConstants.ZERO))
            {
                return this;
            } else
            {
                ECFieldElement TWO = curve.fromBigInteger(BigInteger.valueOf(2L));
                ECFieldElement THREE = curve.fromBigInteger(BigInteger.valueOf(3L));
                ECFieldElement gamma = x.multiply(x).multiply(THREE).add(curve.a).divide(y.multiply(TWO));
                ECFieldElement x3 = gamma.multiply(gamma).subtract(x.multiply(TWO));
                ECFieldElement y3 = gamma.multiply(x.subtract(x3)).subtract(y);
                return new Fp(curve, x3, y3);
            }
        }

        public ECPoint subtract(ECPoint p2)
        {
            return add(new Fp(curve, p2.x, p2.y.negate()));
        }

        public ECPoint multiply(BigInteger k)
        {
            BigInteger e = k;
            BigInteger h = e.multiply(BigInteger.valueOf(3L));
            ECPoint R = this;
            for(int i = h.bitLength() - 2; i > 0; i--)
            {
                R = R.twice();
                if(h.testBit(i) && !e.testBit(i))
                {
                    R = R.add(this);
                    continue;
                }
                if(!h.testBit(i) && e.testBit(i))
                    R = R.subtract(this);
            }

            return R;
        }

        public Fp(ECCurve curve, ECFieldElement x, ECFieldElement y)
        {
            super(curve, x, y);
        }
    }


    ECCurve curve;
    ECFieldElement x;
    ECFieldElement y;

    protected ECPoint(ECCurve curve, ECFieldElement x, ECFieldElement y)
    {
        this.curve = curve;
        this.x = x;
        this.y = y;
    }

    public ECFieldElement getX()
    {
        return x;
    }

    public ECFieldElement getY()
    {
        return y;
    }

    public boolean equals(Object other)
    {
        if(other == this)
            return true;
        if(!(other instanceof ECPoint))
        {
            return false;
        } else
        {
            ECPoint o = (ECPoint)other;
            return x.equals(o.x) && y.equals(o.y);
        }
    }

    public abstract byte[] getEncoded();

    public abstract byte[] getEncoded(boolean flag);

    public abstract ECPoint add(ECPoint ecpoint);

    public abstract ECPoint subtract(ECPoint ecpoint);

    public abstract ECPoint twice();

    public abstract ECPoint multiply(BigInteger biginteger);
}