deskeygenerator.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: DESKeyGenerator.java,v 1.14 1998/10/29 06:16:09 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/DESKeyGenerator.java,v $
 * $Revision: 1.14 $
 * $Date: 1998/10/29 06:16:09 $
 * $State: Exp $
 */

import java.security.InvalidAlgorithmParameterException;
import java.security.spec.AlgorithmParameterSpec;
import java.security.SecureRandom;
import java.security.InvalidKeyException;
import javax.crypto.KeyGeneratorSpi;
import javax.crypto.SecretKey;
import javax.crypto.spec.DESKeySpec;

/**
 * This class is used for generating random DES keys.  This class
 * should not be instantiated directly, instead use the
 * javax.crypto.KeyGenerator interface.
 * <p>
 * There is no AlgorithmParameterSpec class defined for DES 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 DESKeyGenerator extends KeyGeneratorSpi
{
	public final static String ident = "$Id: DESKeyGenerator.java,v 1.14 1998/10/29 06:16:09 leachbj Exp $";

	SecureRandom		rand;

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

		// generate random non-weak key
		byte[] bytes = new byte[DESKeySpec.DES_KEY_LEN];

		DESKey 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))
				{
					key = new DESKey(bytes);

					// clear the key from the byte buffer
					for (int i = 0;
						i < DESKeySpec.DES_KEY_LEN; i++)
					{
						bytes[i] = 0;
					}
				}
			}
			catch (InvalidKeyException e)
			{
				// strictly speaking this can never happen
				// but just in case...
				throw new RuntimeException(
						"DESKeyGenerator: " + e);
			}
		} while (key == null);

		return key;
	}
	/**
	 * Since DES keys are of a fixed size, this method does
	 * nothing except set the random source.
	 *
	 * @param strength the strength of the key. This parameter is
	 * 	ignored.
	 * @param random the source of randomness for this key generator
	 */
	protected void engineInit(
		int		strength,
		SecureRandom	random)
	{
		rand = random;
	}
	/**
	 * Initialises the key generator with the given random number source.
	 *
	 * @param random	a source of random numbers for this generator.
	 */
	protected void engineInit(
		SecureRandom	random)
	{
		rand = random;
	}
	/**
	 * This method is not implemented as there is no AlgorithmParameterSpec
	 * defined for DES.  (Use one of the other initialisation methods!)
	 *
	 * @param params	the algorithm parameter specs for this
	 *		generator.
	 * @param random	a source of random numbers for this generator.
	 * @exception InvalidAlgorithmParameterException	An invalid
	* 	parameter specification is provided.
	 */
	protected void engineInit(
		AlgorithmParameterSpec	params,
		SecureRandom		random)
		throws InvalidAlgorithmParameterException
	{
		throw new InvalidAlgorithmParameterException("Not Implemented");
	}
	/**
	 * DES Keys use the LSB as the odd parity bit.  This can
	 * be used to check for corrupt keys.
	 *
	 * @param bytes the byte array to set the parity on.
	 */
	protected void setOddParity(byte[] bytes)
	{
		for (int i = 0; i < bytes.length; i++)
		{
			int b = bytes[i];
			bytes[i] = (byte)((b & 0xfe) |
				(((b >> 1) ^
				(b >> 2) ^
				(b >> 3) ^
				(b >> 4) ^
				(b >> 5) ^
				(b >> 6) ^
				(b >> 7)) ^ 0x01));
		}
	}
}