GenSig.java Source code

Introduction

Here is the source code for GenSig.java

Source

/* 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());
            }

    };

}