import java.math.BigInteger;
import java.security.KeyFactory;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.Signature;
import java.security.interfaces.DSAParams;
import java.security.interfaces.DSAPrivateKey;
import java.security.interfaces.DSAPublicKey;
import java.security.spec.DSAPrivateKeySpec;
import java.security.spec.DSAPublicKeySpec;
import java.security.spec.KeySpec;
public class Main {
public static void main(String[] argv) throws Exception {
KeyPairGenerator keyGen = KeyPairGenerator.getInstance("DSA");
keyGen.initialize(1024);
KeyPair keypair = keyGen.genKeyPair();
DSAPrivateKey privateKey = (DSAPrivateKey) keypair.getPrivate();
DSAPublicKey publicKey = (DSAPublicKey) keypair.getPublic();
DSAParams dsaParams = privateKey.getParams();
BigInteger p = dsaParams.getP();
BigInteger q = dsaParams.getQ();
BigInteger g = dsaParams.getG();
BigInteger x = privateKey.getX();
BigInteger y = publicKey.getY();
KeyFactory keyFactory = KeyFactory.getInstance("DSA");
KeySpec publicKeySpec = new DSAPublicKeySpec(y, p, q, g);
PublicKey publicKey1 = keyFactory.generatePublic(publicKeySpec);
KeySpec privateKeySpec = new DSAPrivateKeySpec(x, p, q, g);
PrivateKey privateKey1 = keyFactory.generatePrivate(privateKeySpec);
byte[] buffer = new byte[1024];
Signature sig = Signature.getInstance(privateKey1.getAlgorithm());
sig.initSign(privateKey1);
sig.update(buffer, 0, buffer.length);
byte[] signature = sig.sign();
sig = Signature.getInstance(publicKey1.getAlgorithm());
sig.initVerify(publicKey1);
sig.update(buffer, 0, buffer.length);
sig.verify(signature);
}
}