DSA signature Verify - Java Security

Java examples for Security:DSA

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Description

DSA signature Verify

Demo Code

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

class VerSig {/*from ww w .ja v a 2s  .c  o m*/

    public static void main(String[] args) {

        /* Verify a DSA signature */

        if (args.length != 3) {
            System.out
                    .println("Usage: VerSig publickeyfile signaturefile datafile");
        } else
            try {

                /* import encoded public key */

                FileInputStream keyfis = new FileInputStream(args[0]);
                byte[] encKey = new byte[keyfis.available()];
                keyfis.read(encKey);

                keyfis.close();

                X509EncodedKeySpec pubKeySpec = new X509EncodedKeySpec(
                        encKey);

                KeyFactory keyFactory = KeyFactory
                        .getInstance("DSA", "SUN");
                PublicKey pubKey = keyFactory.generatePublic(pubKeySpec);

                /* input the signature bytes */
                FileInputStream sigfis = new FileInputStream(args[1]);
                byte[] sigToVerify = new byte[sigfis.available()];
                sigfis.read(sigToVerify);

                sigfis.close();

                /* create a Signature object and initialize it with the public key */
                Signature sig = Signature.getInstance("SHA1withDSA", "SUN");
                sig.initVerify(pubKey);

                /* Update and verify the data */

                FileInputStream datafis = new FileInputStream(args[2]);
                BufferedInputStream bufin = new BufferedInputStream(datafis);

                byte[] buffer = new byte[1024];
                int len;
                while (bufin.available() != 0) {
                    len = bufin.read(buffer);
                    sig.update(buffer, 0, len);
                }
                ;

                bufin.close();

                boolean verifies = sig.verify(sigToVerify);

                System.out.println("signature verifies: " + verifies);

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

    }

}

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 *     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,
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 * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
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