Java example source code file (DHKeyAgreement2.java)

This example Java source code file (DHKeyAgreement2.java) is included in the alvinalexander.com "Java Source Code Warehouse" project. The intent of this project is to help you "Learn Java by Example" ^TM.

Learn more about this Java project at its project page.

Java - Java tags/keywords

algorithmparameters, biginteger, crypto, dhkeyagreement2, dhparameterspec, different, exception, generate_dh_params, keyfactory, keypairgenerator, math, publickey, security, stringbuffer, sunjce, x509encodedkeyspec

The DHKeyAgreement2.java Java example source code

/*
 * Copyright (c) 1997, 2012, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

/*
 * @test
 * @bug 7146728
 * @summary DHKeyAgreement2
 * @author Jan Luehe
 */

import java.io.*;
import java.math.BigInteger;
import java.security.*;
import java.security.spec.*;
import java.security.interfaces.*;
import javax.crypto.*;
import javax.crypto.spec.*;
import javax.crypto.interfaces.*;
import com.sun.crypto.provider.SunJCE;

import sun.misc.HexDumpEncoder;

/**
 * This test utility executes the Diffie-Hellman key agreement protocol
 * between 2 parties: Alice and Bob.
 *
 * By default, preconfigured parameters (1024 bit prime modulus and base
 * generator used by SKIP) are used.
 * If this program is called with the "-gen" option, a new set of parameters
 * are created.
 */

public class DHKeyAgreement2 {

    private static final String SUNJCE = "SunJCE";
    private DHKeyAgreement2() {}

    public static void main(String argv[]) throws Exception {
            String mode = "USE_SKIP_DH_PARAMS";

            DHKeyAgreement2 keyAgree = new DHKeyAgreement2();

            if (argv.length > 1) {
                keyAgree.usage();
                throw new Exception("Wrong number of command options");
            } else if (argv.length == 1) {
                if (!(argv[0].equals("-gen"))) {
                    keyAgree.usage();
                    throw new Exception("Unrecognized flag: " + argv[0]);
                }
                mode = "GENERATE_DH_PARAMS";
            }

            keyAgree.run(mode);
            System.out.println("Test Passed");
    }

    private void run(String mode) throws Exception {

        DHParameterSpec dhSkipParamSpec;

        if (mode.equals("GENERATE_DH_PARAMS")) {
            // Some central authority creates new DH parameters
            System.err.println("Creating Diffie-Hellman parameters ...");
            AlgorithmParameterGenerator paramGen
                = AlgorithmParameterGenerator.getInstance("DH", SUNJCE);
            paramGen.init(512);
            AlgorithmParameters params = paramGen.generateParameters();
            dhSkipParamSpec = (DHParameterSpec)params.getParameterSpec
                (DHParameterSpec.class);
        } else {
            // use some pre-generated, default DH parameters
            System.err.println("Using SKIP Diffie-Hellman parameters");
            dhSkipParamSpec = new DHParameterSpec(skip1024Modulus,
                                                  skip1024Base);
        }

        /*
         * Alice creates her own DH key pair, using the DH parameters from
         * above
         */
        System.err.println("ALICE: Generate DH keypair ...");
        KeyPairGenerator aliceKpairGen = KeyPairGenerator.getInstance("DH", SUNJCE);
        aliceKpairGen.initialize(dhSkipParamSpec);
        KeyPair aliceKpair = aliceKpairGen.generateKeyPair();
        System.out.println("Alice DH public key:\n" +
                           aliceKpair.getPublic().toString());
        System.out.println("Alice DH private key:\n" +
                           aliceKpair.getPrivate().toString());
        DHParameterSpec dhParamSpec =
            ((DHPublicKey)aliceKpair.getPublic()).getParams();
        AlgorithmParameters algParams = AlgorithmParameters.getInstance("DH", SUNJCE);
        algParams.init(dhParamSpec);
        System.out.println("Alice DH parameters:\n"
                           + algParams.toString());

        // Alice executes Phase1 of her version of the DH protocol
        System.err.println("ALICE: Execute PHASE1 ...");
        KeyAgreement aliceKeyAgree = KeyAgreement.getInstance("DH", SUNJCE);
        aliceKeyAgree.init(aliceKpair.getPrivate());

        // Alice encodes her public key, and sends it over to Bob.
        byte[] alicePubKeyEnc = aliceKpair.getPublic().getEncoded();

        /*
         * Let's turn over to Bob. Bob has received Alice's public key
         * in encoded format.
         * He instantiates a DH public key from the encoded key material.
         */
        KeyFactory bobKeyFac = KeyFactory.getInstance("DH", SUNJCE);
        X509EncodedKeySpec x509KeySpec = new X509EncodedKeySpec
            (alicePubKeyEnc);
        PublicKey alicePubKey = bobKeyFac.generatePublic(x509KeySpec);

        /*
         * Bob gets the DH parameters associated with Alice's public key.
         * He must use the same parameters when he generates his own key
         * pair.
         */
        dhParamSpec = ((DHPublicKey)alicePubKey).getParams();

        // Bob creates his own DH key pair
        System.err.println("BOB: Generate DH keypair ...");
        KeyPairGenerator bobKpairGen = KeyPairGenerator.getInstance("DH", SUNJCE);
        bobKpairGen.initialize(dhParamSpec);
        KeyPair bobKpair = bobKpairGen.generateKeyPair();
        System.out.println("Bob DH public key:\n" +
                           bobKpair.getPublic().toString());
        System.out.println("Bob DH private key:\n" +
                           bobKpair.getPrivate().toString());

        // Bob executes Phase1 of his version of the DH protocol
        System.err.println("BOB: Execute PHASE1 ...");
        KeyAgreement bobKeyAgree = KeyAgreement.getInstance("DH", SUNJCE);
        bobKeyAgree.init(bobKpair.getPrivate());

        // Bob encodes his public key, and sends it over to Alice.
        byte[] bobPubKeyEnc = bobKpair.getPublic().getEncoded();

        /*
         * Alice uses Bob's public key for Phase2 of her version of the DH
         * protocol.
         * Before she can do so, she has to instanticate a DH public key
         * from Bob's encoded key material.
         */
        KeyFactory aliceKeyFac = KeyFactory.getInstance("DH", SUNJCE);
        x509KeySpec = new X509EncodedKeySpec(bobPubKeyEnc);
        PublicKey bobPubKey = aliceKeyFac.generatePublic(x509KeySpec);
        System.err.println("ALICE: Execute PHASE2 ...");
        aliceKeyAgree.doPhase(bobPubKey, true);

        /*
         * Bob uses Alice's public key for Phase2 of his version of the DH
         * protocol.
         */
        System.err.println("BOB: Execute PHASE2 ...");
        bobKeyAgree.doPhase(alicePubKey, true);

        /*
         * At this stage, both Alice and Bob have completed the DH key
         * agreement protocol.
         * Each generates the (same) shared secret.
         */
        byte[] aliceSharedSecret = aliceKeyAgree.generateSecret();
        int aliceLen = aliceSharedSecret.length;

        // check if alice's key agreement has been reset afterwards
        try {
            aliceKeyAgree.generateSecret();
            throw new Exception("Error: alice's KeyAgreement not reset");
        } catch (IllegalStateException e) {
            System.out.println("EXPECTED:  " + e.getMessage());
        }

        byte[] bobSharedSecret = new byte[aliceLen];
        int bobLen;
        try {
            // provide output buffer that is too short
            bobLen = bobKeyAgree.generateSecret(bobSharedSecret, 1);
        } catch (ShortBufferException e) {
            System.out.println("EXPECTED:  " + e.getMessage());
        }
        // retry w/ output buffer of required size
        bobLen = bobKeyAgree.generateSecret(bobSharedSecret, 0);

        // check if bob's key agreement has been reset afterwards
        try {
            bobKeyAgree.generateSecret(bobSharedSecret, 0);
            throw new Exception("Error: bob's KeyAgreement not reset");
        } catch (IllegalStateException e) {
            System.out.println("EXPECTED:  " + e.getMessage());
        }

        System.out.println("Alice secret: " + toHexString(aliceSharedSecret));
        System.out.println("Bob secret: " + toHexString(bobSharedSecret));

        if (aliceLen != bobLen) {
            throw new Exception("Shared secrets have different lengths");
        }
        for (int i=0; i<aliceLen; i++) {
            if (aliceSharedSecret[i] != bobSharedSecret[i]) {
                throw new Exception("Shared secrets differ");
            }
        }
        System.err.println("Shared secrets are the same");

        // Now let's return the shared secret as a SecretKey object
        // and use it for encryption
        System.out.println("Return shared secret as SecretKey object ...");
        bobKeyAgree.doPhase(alicePubKey, true);
        SecretKey desKey = bobKeyAgree.generateSecret("DES");

        Cipher desCipher = Cipher.getInstance("DES/ECB/PKCS5Padding");
        desCipher.init(Cipher.ENCRYPT_MODE, desKey);

        byte[] cleartext = "This is just an example".getBytes();
        byte[] ciphertext = desCipher.doFinal(cleartext);

        desCipher.init(Cipher.DECRYPT_MODE, desKey);
        byte[] cleartext1 = desCipher.doFinal(ciphertext);

        int clearLen = cleartext.length;
        int clear1Len = cleartext1.length;
        if (clearLen != clear1Len) {
            throw new Exception("DIFFERENT");
        }
        for (int i=0; i < clear1Len; i++) {
            if (cleartext[i] != cleartext1[i]) {
                throw new Exception("DIFFERENT");
            }
        }
        System.err.println("SAME");
    }

    /*
     * Converts a byte to hex digit and writes to the supplied buffer
     */
    private void byte2hex(byte b, StringBuffer buf) {
        char[] hexChars = { '0', '1', '2', '3', '4', '5', '6', '7', '8',
                            '9', 'A', 'B', 'C', 'D', 'E', 'F' };
        int high = ((b & 0xf0) >> 4);
        int low = (b & 0x0f);
        buf.append(hexChars[high]);
        buf.append(hexChars[low]);
    }

    /*
     * Converts a byte array to hex string
     */
    private String toHexString(byte[] block) {
        StringBuffer buf = new StringBuffer();

        int len = block.length;

        for (int i = 0; i < len; i++) {
             byte2hex(block[i], buf);
             if (i < len-1) {
                 buf.append(":");
             }
        }
        return buf.toString();
    }

    /*
     * Prints the usage of this test.
     */
    private void usage() {
        System.err.print("DHKeyAgreement usage: ");
        System.err.println("[-gen]");
    }

    // The 1024 bit Diffie-Hellman modulus values used by SKIP
    private static final byte skip1024ModulusBytes[] = {
        (byte)0xF4, (byte)0x88, (byte)0xFD, (byte)0x58,
        (byte)0x4E, (byte)0x49, (byte)0xDB, (byte)0xCD,
        (byte)0x20, (byte)0xB4, (byte)0x9D, (byte)0xE4,
        (byte)0x91, (byte)0x07, (byte)0x36, (byte)0x6B,
        (byte)0x33, (byte)0x6C, (byte)0x38, (byte)0x0D,
        (byte)0x45, (byte)0x1D, (byte)0x0F, (byte)0x7C,
        (byte)0x88, (byte)0xB3, (byte)0x1C, (byte)0x7C,
        (byte)0x5B, (byte)0x2D, (byte)0x8E, (byte)0xF6,
        (byte)0xF3, (byte)0xC9, (byte)0x23, (byte)0xC0,
        (byte)0x43, (byte)0xF0, (byte)0xA5, (byte)0x5B,
        (byte)0x18, (byte)0x8D, (byte)0x8E, (byte)0xBB,
        (byte)0x55, (byte)0x8C, (byte)0xB8, (byte)0x5D,
        (byte)0x38, (byte)0xD3, (byte)0x34, (byte)0xFD,
        (byte)0x7C, (byte)0x17, (byte)0x57, (byte)0x43,
        (byte)0xA3, (byte)0x1D, (byte)0x18, (byte)0x6C,
        (byte)0xDE, (byte)0x33, (byte)0x21, (byte)0x2C,
        (byte)0xB5, (byte)0x2A, (byte)0xFF, (byte)0x3C,
        (byte)0xE1, (byte)0xB1, (byte)0x29, (byte)0x40,
        (byte)0x18, (byte)0x11, (byte)0x8D, (byte)0x7C,
        (byte)0x84, (byte)0xA7, (byte)0x0A, (byte)0x72,
        (byte)0xD6, (byte)0x86, (byte)0xC4, (byte)0x03,
        (byte)0x19, (byte)0xC8, (byte)0x07, (byte)0x29,
        (byte)0x7A, (byte)0xCA, (byte)0x95, (byte)0x0C,
        (byte)0xD9, (byte)0x96, (byte)0x9F, (byte)0xAB,
        (byte)0xD0, (byte)0x0A, (byte)0x50, (byte)0x9B,
        (byte)0x02, (byte)0x46, (byte)0xD3, (byte)0x08,
        (byte)0x3D, (byte)0x66, (byte)0xA4, (byte)0x5D,
        (byte)0x41, (byte)0x9F, (byte)0x9C, (byte)0x7C,
        (byte)0xBD, (byte)0x89, (byte)0x4B, (byte)0x22,
        (byte)0x19, (byte)0x26, (byte)0xBA, (byte)0xAB,
        (byte)0xA2, (byte)0x5E, (byte)0xC3, (byte)0x55,
        (byte)0xE9, (byte)0x2F, (byte)0x78, (byte)0xC7
    };

    // The SKIP 1024 bit modulus
    private static final BigInteger skip1024Modulus
    = new BigInteger(1, skip1024ModulusBytes);

    // The base used with the SKIP 1024 bit modulus
    private static final BigInteger skip1024Base = BigInteger.valueOf(2);
}