package org.bouncycastle.crypto.generators;
import org.bouncycastle.crypto.AsymmetricCipherKeyPair;
import org.bouncycastle.crypto.AsymmetricCipherKeyPairGenerator;
import org.bouncycastle.crypto.KeyGenerationParameters;
import org.bouncycastle.crypto.params.DSAKeyGenerationParameters;
import org.bouncycastle.crypto.params.DSAParameters;
import org.bouncycastle.crypto.params.DSAPrivateKeyParameters;
import org.bouncycastle.crypto.params.DSAPublicKeyParameters;
import java.math.BigInteger;
import java.security.SecureRandom;
/**
* a DSA key pair generator.
*
* This generates DSA keys in line with the method described
* in FIPS 186-2.
*/
public class DSAKeyPairGenerator
implements AsymmetricCipherKeyPairGenerator
{
private static final BigInteger ZERO = BigInteger.valueOf(0);
private DSAKeyGenerationParameters param;
public void init(
KeyGenerationParameters param)
{
this.param = (DSAKeyGenerationParameters)param;
}
public AsymmetricCipherKeyPair generateKeyPair()
{
BigInteger p, q, g, x, y;
DSAParameters dsaParams = param.getParameters();
SecureRandom random = param.getRandom();
q = dsaParams.getQ();
p = dsaParams.getP();
g = dsaParams.getG();
do
{
x = new BigInteger(160, random);
}
while (x.equals(ZERO) || x.compareTo(q) >= 0);
//
// calculate the public key.
//
y = g.modPow(x, p);
return new AsymmetricCipherKeyPair(
new DSAPublicKeyParameters(y, dsaParams),
new DSAPrivateKeyParameters(x, dsaParams));
}
}