Generate a DSA signature : Signature « Security « Java





Generate a DSA signature

 
/* From http://java.sun.com/docs/books/tutorial/index.html */

/*
 * Copyright (c) 2006 Sun Microsystems, Inc. All Rights Reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 * -Redistribution of source code must retain the above copyright notice, this
 *  list of conditions and the following disclaimer.
 *
 * -Redistribution in binary form must reproduce the above copyright notice,
 *  this list of conditions and the following disclaimer in the documentation
 *  and/or other materials provided with the distribution.
 *
 * Neither the name of Sun Microsystems, Inc. or the names of contributors may
 * be used to endorse or promote products derived from this software without
 * specific prior written permission.
 *
 * This software is provided "AS IS," without a warranty of any kind. ALL
 * EXPRESS OR IMPLIED CONDITIONS, REPRESENTATIONS AND WARRANTIES, INCLUDING
 * ANY IMPLIED WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE
 * OR NON-INFRINGEMENT, ARE HEREBY EXCLUDED. SUN MIDROSYSTEMS, INC. ("SUN")
 * AND ITS LICENSORS SHALL NOT BE LIABLE FOR ANY DAMAGES SUFFERED BY LICENSEE
 * AS A RESULT OF USING, MODIFYING OR DISTRIBUTING THIS SOFTWARE OR ITS
 * DERIVATIVES. IN NO EVENT WILL SUN OR ITS LICENSORS BE LIABLE FOR ANY LOST
 * REVENUE, PROFIT OR DATA, OR FOR DIRECT, INDIRECT, SPECIAL, CONSEQUENTIAL,
 * INCIDENTAL OR PUNITIVE DAMAGES, HOWEVER CAUSED AND REGARDLESS OF THE THEORY
 * OF LIABILITY, ARISING OUT OF THE USE OF OR INABILITY TO USE THIS SOFTWARE,
 * EVEN IF SUN HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.
 *
 * You acknowledge that this software is not designed, licensed or intended
 * for use in the design, construction, operation or maintenance of any
 * nuclear facility.
 */

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.security.KeyPair;
import java.security.KeyPairGenerator;
import java.security.PrivateKey;
import java.security.PublicKey;
import java.security.SecureRandom;
import java.security.Signature;

public class GenSig {

  public static void main(String[] args) {

    /* Generate a DSA signature */

    if (args.length != 1) {
      System.out.println("Usage: GenSig nameOfFileToSign");
    } else
      try {

        /* Generate a key pair */

        KeyPairGenerator keyGen = KeyPairGenerator.getInstance("DSA",
            "SUN");
        SecureRandom random = SecureRandom.getInstance("SHA1PRNG",
            "SUN");

        keyGen.initialize(1024, random);

        KeyPair pair = keyGen.generateKeyPair();
        PrivateKey priv = pair.getPrivate();
        PublicKey pub = pair.getPublic();

        /*
         * Create a Signature object and initialize it with the private
         * key
         */

        Signature dsa = Signature.getInstance("SHA1withDSA", "SUN");

        dsa.initSign(priv);

        /* Update and sign the data */

        FileInputStream fis = new FileInputStream(args[0]);
        BufferedInputStream bufin = new BufferedInputStream(fis);
        byte[] buffer = new byte[1024];
        int len;
        while (bufin.available() != 0) {
          len = bufin.read(buffer);
          dsa.update(buffer, 0, len);
        }
        ;

        bufin.close();

        /*
         * Now that all the data to be signed has been read in, generate
         * a signature for it
         */

        byte[] realSig = dsa.sign();

        /* Save the signature in a file */
        FileOutputStream sigfos = new FileOutputStream("sig");
        sigfos.write(realSig);

        sigfos.close();

        /* Save the public key in a file */
        byte[] key = pub.getEncoded();
        FileOutputStream keyfos = new FileOutputStream("suepk");
        keyfos.write(key);

        keyfos.close();

      } catch (Exception e) {
        System.err.println("Caught exception " + e.toString());
      }

  };

}


           
         
  










Related examples in the same category

1.Signature Sign And Verify
2.Verify a DSA signature
3.Test the signature
4.Creating a Signature
5.Verifies the signature for the given buffer of bytes using the public key.
6.Signing a Java Object