keypairgenerator.java

ElGamal method is an aymetric method to crypt message. You can use ElGamal to crypt the key session

package elgamal;

import java.math.BigInteger;
import java.util.Random;

public class KeyPairGenerator
{

    private PublicKey publicKey;
    private PrivateKey privateKey;
    private Parameter params;
    private Random random;
    private int strength;

    public KeyPairGenerator(Random random, Parameter params)
    {
        this.params = params;
        this.random = random;
        strength = params.getP().bitLength() - 1;
        generateKeyPair();
    }

    public PublicKey getPublic()
    {
        return publicKey;
    }

    public PrivateKey getPrivate()
    {
        return privateKey;
    }

    private void generateKeyPair()
    {
        int qLength = strength - 1;
        BigInteger p = params.getP();
        BigInteger g = params.getG();
        BigInteger x = new BigInteger(qLength, random);
        BigInteger y = g.modPow(x, p);
        publicKey = new PublicKey(y, params);
        privateKey = new PrivateKey(x, params);
    }
}