test/com/sun/crypto/provider/KeyAgreement/DHKeyAgreement2.java - toolchain/jdk/jdk9_jdk - Git at Google

 /*
  * Copyright (c) 1997, 2007, 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 0000000
  * @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 DHKeyAgreement2() {}

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

             // Add JCE to the list of providers
             SunJCE jce = new SunJCE();
             Security.addProvider(jce);

             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");
             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");
         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");
         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");
         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");
         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");
         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");
         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");
         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;

         byte[] bobSharedSecret = new byte[aliceLen];
         int bobLen;
         try {
             // provide output buffer that is too short
             bobLen = bobKeyAgree.generateSecret(bobSharedSecret, 1);

             /*
              * Gatekeeper's note:
              * We should not be getting here, but every so often, we
              * get a failure, either a "ShortBufferException" or
              * "Key agreement has not been completed yet" in the
              * generateSecret(bobSharedSecret, 0) below.
              *
              * This will help to figure out why we're dropping through
              * and not failing.
              */
             System.out.println("NIGHTLY:  Should *NOT* be here!!!\n" +
                 "aliceLen = " + aliceLen + "\n" +
                 "Alice's shared secret");

             try {
                 HexDumpEncoder hd = new HexDumpEncoder();

                 hd.encodeBuffer(
                     new ByteArrayInputStream(aliceSharedSecret), System.out);
             } catch (IOException e) { }

             System.out.println("bobLen = " + bobLen);

             try {
                 HexDumpEncoder hd = new HexDumpEncoder();

                 hd.encodeBuffer(
                     new ByteArrayInputStream(bobSharedSecret), System.out);
             } catch (IOException e) { }

             throw new Exception("Shouldn't be succeeding.");
         } catch (ShortBufferException e) {
             System.out.println("EXPECTED:  " + e.getMessage());
         }

         // provide output buffer of required size
         bobLen = bobKeyAgree.generateSecret(bobSharedSecret, 0);

         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);
 }
	/*
	* Copyright (c) 1997, 2007, 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 0000000
	* @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 DHKeyAgreement2() {}

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

	// Add JCE to the list of providers
	SunJCE jce = new SunJCE();
	Security.addProvider(jce);

	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");
	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");
	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");
	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");
	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");
	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");
	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");
	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");
	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;

	byte[] bobSharedSecret = new byte[aliceLen];
	int bobLen;
	try {
	// provide output buffer that is too short
	bobLen = bobKeyAgree.generateSecret(bobSharedSecret, 1);

	/*
	* Gatekeeper's note:
	* We should not be getting here, but every so often, we
	* get a failure, either a "ShortBufferException" or
	* "Key agreement has not been completed yet" in the
	* generateSecret(bobSharedSecret, 0) below.
	*
	* This will help to figure out why we're dropping through
	* and not failing.
	*/
	System.out.println("NIGHTLY: Should NOT be here!!!\n" +
	"aliceLen = " + aliceLen + "\n" +
	"Alice's shared secret");

	try {
	HexDumpEncoder hd = new HexDumpEncoder();

	hd.encodeBuffer(
	new ByteArrayInputStream(aliceSharedSecret), System.out);
	} catch (IOException e) { }

	System.out.println("bobLen = " + bobLen);

	try {
	HexDumpEncoder hd = new HexDumpEncoder();

	hd.encodeBuffer(
	new ByteArrayInputStream(bobSharedSecret), System.out);
	} catch (IOException e) { }

	throw new Exception("Shouldn't be succeeding.");
	} catch (ShortBufferException e) {
	System.out.println("EXPECTED: " + e.getMessage());
	}

	// provide output buffer of required size
	bobLen = bobKeyAgree.generateSecret(bobSharedSecret, 0);

	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);
	}