package org.bouncycastle.crypto.generators;
import java.math.BigInteger;
import org.bouncycastle.crypto.AsymmetricCipherKeyPair;
import org.bouncycastle.crypto.AsymmetricCipherKeyPairGenerator;
import org.bouncycastle.crypto.KeyGenerationParameters;
import org.bouncycastle.crypto.params.DHParameters;
import org.bouncycastle.crypto.params.ElGamalKeyGenerationParameters;
import org.bouncycastle.crypto.params.ElGamalParameters;
import org.bouncycastle.crypto.params.ElGamalPrivateKeyParameters;
import org.bouncycastle.crypto.params.ElGamalPublicKeyParameters;
/**
* a ElGamal key pair generator.
* <p>
* This generates keys consistent for use with ElGamal as described in
* page 164 of "Handbook of Applied Cryptography".
*/
public class ElGamalKeyPairGenerator
implements AsymmetricCipherKeyPairGenerator
{
private ElGamalKeyGenerationParameters param;
public void init(
KeyGenerationParameters param)
{
this.param = (ElGamalKeyGenerationParameters)param;
}
public AsymmetricCipherKeyPair generateKeyPair()
{
DHKeyGeneratorHelper helper = DHKeyGeneratorHelper.INSTANCE;
ElGamalParameters egp = param.getParameters();
DHParameters dhp = new DHParameters(egp.getP(), egp.getG(), null, egp.getL());
BigInteger x = helper.calculatePrivate(dhp, param.getRandom());
BigInteger y = helper.calculatePublic(dhp, x);
return new AsymmetricCipherKeyPair(
new ElGamalPublicKeyParameters(y, egp),
new ElGamalPrivateKeyParameters(x, egp));
}
}