java ec

package A;

import java.math.BigInteger;

public class Ec implements Curve {
    public Ec(BigInteger p, BigInteger n, BigInteger b, BigInteger gx, BigInteger gy, int bitsize, String name) {
        P = p;
        N = n;
        B = b;
        Gx = gx;
        Gy = gy;
        BitSize = bitsize;
        Name = name;
    }
    private BigInteger P, N, B, Gx, Gy;
    private int BitSize;
    private String Name;

    @Override
    public CurveParams Params() {
        return new CurveParams(P, N, B, Gx, Gy, BitSize, Name);
    }

    @Override
    public boolean IsOnCurve(BigInteger x, BigInteger y) {
        return false;
    }

    @Override
    public Point Add(Point a, Point b) {
        BigInteger k = a.x.subtract(b.x).mod(P).modInverse(P).multiply(a.y.subtract(b.y));
        BigInteger x = k.multiply(k).subtract(a.x.add(b.x)).mod(P);
        return new Point(x, k.multiply(a.x.subtract(x)).subtract(a.y).mod(P));
    }

    @Override
    public Point Double(Point a) {
        BigInteger k = a.y.multiply(BigInteger.valueOf(2)).mod(P).modInverse(P).multiply(a.x.multiply(a.x).multiply(BigInteger.valueOf(3)).subtract(BigInteger.valueOf(3)));
        BigInteger x = k.multiply(k).subtract(a.x.add(a.x)).mod(P);
        return new Point(x, k.multiply(a.x.subtract(x)).subtract(a.y).mod(P));
    }

    @Override
    public Point ScalarBaseMult(BigInteger k) {
        return ScalarMult(new Point(Gx, Gy), k);
    }

    @Override
    public Point ScalarMult(Point p, BigInteger k) {
        byte[] b = k.toByteArray();
        Point g = p;
        Point r = null;
        for (int j = 0; j < b.length; j++) {
            int t = b[j] & 0xff;
            for (int i = 0; i < 8; i++) {
                if (r != null)
                    r = Double(r);
                if ((t & 0x80) == 0x80) {
                    if (r == null)
                        r = g;
                    else
                        r = Add(r, g);
                }
                t <<= 1;
            }
        }
        return r;
    }

    @Override
    public BigInteger Inverse(BigInteger k) {
        return k.modInverse(N);
    }

    @Override
    public Point CombinedMult(Point p, BigInteger baseScalar, BigInteger scalar) {
        Point a = ScalarBaseMult(baseScalar);
        Point b = ScalarMult(p, scalar);
        if (a.x.compareTo(b.x) == 0 && a.y.compareTo(b.y) == 0)
            return Double(a);
        return Add(a, b);
    }
}