desedekeygenerator.java

面向应用的智能安全代理平台和工具包是一个综合网络应用的安全共性需求而设计和实现的一个通用性的网络信息安全应用支撑平台

package au.net.aba.crypto.provider;

/*
 * $Id: DESedeKeyGenerator.java,v 1.10 1999/02/17 04:31:52 leachbj Exp $
 * $Author: leachbj $
 *
 * Copyright (C) 1996-1998 Australian Business Access Pty Ltd.
 * All rights reserved.
 * 
 * Use, modification, copying and distribution of this software is subject the
 * terms and conditions of the ABA Public Licence. See the file
 * "PUBLIC_LICENCE" for additional information.
 *
 * If you have not received a copy of the Public Licence, you must destroy all
 * copies of this file immediately. 
 *
 * $Source: /aba/CVSROOT/jdk1.1/src/au.net.aba/crypto/provider/DESedeKeyGenerator.java,v $
 * $Revision: 1.10 $
 * $Date: 1999/02/17 04:31:52 $
 * $State: Exp $
 */

import java.security.SecureRandom;
import java.security.InvalidKeyException;
import javax.crypto.SecretKey;
import javax.crypto.spec.DESKeySpec;
import javax.crypto.spec.DESedeKeySpec;

/**
 * This class is used for generating random DESede keys.  This class
 * should not be instantiated directly, instead use the
 * javax.crypto.KeyGenerator interface.
 * <p>
 * There is no AlgorithmParameterSpec class defined for DESede so this
 * generator can only be initialised using the keysize,random
 * initialisation.
 * <p>
 * The returned key will be a non-weak key with odd parity.
 */
public class DESedeKeyGenerator extends DESKeyGenerator
{
	public final static String ident = "$Id: DESedeKeyGenerator.java,v 1.10 1999/02/17 04:31:52 leachbj Exp $";

	/**
	 * Generates a secret key, setting odd parity and checking that the
	 * key is not a weak key.
	 *
	 * @return a DESede key object.
	 */
	protected SecretKey engineGenerateKey()
	{
		/*
		 * use a default random source if none was provided
		 */
		if (rand == null)
		{
			rand = new SecureRandom();
		}

		// generate random non-weak key
		int	count = 0;
		byte[]	keyBytes = new byte[DESedeKeySpec.DES_EDE_KEY_LEN];
		byte[]	bytes = new byte[DESedeKeySpec.DES_EDE_KEY_LEN];

		DESedeKey key = null;

		do
		{
			// get 64 bits of random data, 8 bits are wasted :(
			rand.nextBytes(bytes);

			// set the parity to odd
			setOddParity(bytes);

			// check for weak keys
			try
			{
				if (DESKeySpec.isWeak(bytes, 0))
				{
					continue;
				}
			}
			catch (InvalidKeyException e)
			{
				// strictly speaking this can never happen
				// but just in case...
				throw new RuntimeException(
						"DESedeKeyGenerator: " + e);
			}

			System.arraycopy(bytes, 0, keyBytes,
					count++ * DESKeySpec.DES_KEY_LEN,
					DESKeySpec.DES_KEY_LEN);

			/*
			 * clear the key from the
			 * byte buffer
			 */
			for (int i = 0; i < DESKeySpec.DES_KEY_LEN; i++)
			{
				bytes[i] = 0;
			}

			if (count == 3)
			{
				key = new DESedeKey(keyBytes);

				/*
				 * clear the key from the
				 * byte buffer
				 */
				for (int i = 0;
					i < DESedeKeySpec.DES_EDE_KEY_LEN; i++)
				{
					keyBytes[i] = 0;
				}
			}
		}
		while (key == null);

		return key;
	}
}