java DSA Signature Sign And Verify

SignatureSignAndVerify

import java.security.KeyPair;

import java.security.KeyPairGenerator;

import java.security.PrivateKey;

import java.security.PublicKey;

import java.security.SecureRandom;

import java.security.Security;

import java.security.Signature;



public class SignatureSignAndVerify {



      public static void main(String args[]) throws Exception {

        Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());



        KeyPair keyPair = generateKeyPair(999);



        byte[] data = { 65, 66, 67, 68, 69, 70, 71, 72, 73, 74 };

        byte[] digitalSignature = signData(data, keyPair.getPrivate());



        boolean verified;



        verified = verifySig(data, keyPair.getPublic(), digitalSignature);

        System.out.println(verified) ;



        keyPair = generateKeyPair(888);

        verified = verifySig(data, keyPair.getPublic(), digitalSignature);

        System.out.println(verified);



      }



      public static byte[] signData(byte[] data, PrivateKey key) throws Exception {

        Signature signer = Signature.getInstance("SHA1withDSA");

        signer.initSign(key);

        signer.update(data);

        return (signer.sign());

      }



      public static boolean verifySig(byte[] data, PublicKey key, byte[] sig) throws Exception {

        Signature signer = Signature.getInstance("SHA1withDSA");

        signer.initVerify(key);

        signer.update(data);

        return (signer.verify(sig));



      }



      public static KeyPair generateKeyPair(long seed) throws Exception {

        Security.addProvider(new org.bouncycastle.jce.provider.BouncyCastleProvider());

        KeyPairGenerator keyGenerator = KeyPairGenerator.getInstance("DSA");

        SecureRandom rng = SecureRandom.getInstance("SHA1PRNG", "SUN");

        rng.setSeed(seed);

        keyGenerator.initialize(1024, rng);



        return (keyGenerator.generateKeyPair());

      }

}