DSA signature Generate - Java Security

Java examples for Security:DSA

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Description

DSA signature Generate

Demo Code

import java.io.*;
import java.security.*;

class GenSig {/*from ww w  . j  ava  2  s  .com*/

    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());
            }

    };

}

/*
 * Copyright (c) 1995, 2008, Oracle and/or its affiliates. All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *   - Redistributions of source code must retain the above copyright
 *     notice, this list of conditions and the following disclaimer.
 *
 *   - Redistributions 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 Oracle or the names of its
 *     contributors may be used to endorse or promote products derived
 *     from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
 * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

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