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.DHKeyGenerationParameters;
import org.bouncycastle.crypto.params.DHParameters;
import org.bouncycastle.crypto.params.DHPrivateKeyParameters;
import org.bouncycastle.crypto.params.DHPublicKeyParameters;
/**
* a Diffie-Helman key pair generator.
*
* This generates keys consistent for use in the MTI/A0 key agreement protocol
* as described in "Handbook of Applied Cryptography", Pages 516-519.
*/
public class DHKeyPairGenerator
implements AsymmetricCipherKeyPairGenerator
{
private DHKeyGenerationParameters param;
public void init(
KeyGenerationParameters param)
{
this.param = (DHKeyGenerationParameters)param;
}
public AsymmetricCipherKeyPair generateKeyPair()
{
BigInteger p, g, x, y;
int qLength = param.getStrength() - 1;
DHParameters dhParams = param.getParameters();
p = dhParams.getP();
g = dhParams.getG();
//
// calculate the private key
//
x = new BigInteger(qLength, param.getRandom());
//
// calculate the public key.
//
y = g.modPow(x, p);
return new AsymmetricCipherKeyPair(
new DHPublicKeyParameters(y, dhParams),
new DHPrivateKeyParameters(x, dhParams));
}
}