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    1   /*
    2    * Copyright (c) 1999, 2009, Oracle and/or its affiliates. All rights reserved.
    3    * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
    4    *
    5    * This code is free software; you can redistribute it and/or modify it
    6    * under the terms of the GNU General Public License version 2 only, as
    7    * published by the Free Software Foundation.  Oracle designates this
    8    * particular file as subject to the "Classpath" exception as provided
    9    * by Oracle in the LICENSE file that accompanied this code.
   10    *
   11    * This code is distributed in the hope that it will be useful, but WITHOUT
   12    * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
   13    * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
   14    * version 2 for more details (a copy is included in the LICENSE file that
   15    * accompanied this code).
   16    *
   17    * You should have received a copy of the GNU General Public License version
   18    * 2 along with this work; if not, write to the Free Software Foundation,
   19    * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
   20    *
   21    * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
   22    * or visit www.oracle.com if you need additional information or have any
   23    * questions.
   24    */
   25   
   26   package com.sun.crypto.provider;
   27   
   28   import java.security.SecureRandom;
   29   import java.security.InvalidParameterException;
   30   import java.security.InvalidAlgorithmParameterException;
   31   import java.security.spec.AlgorithmParameterSpec;
   32   import javax.crypto.KeyGeneratorSpi;
   33   import javax.crypto.SecretKey;
   34   import javax.crypto.spec.SecretKeySpec;
   35   
   36   /**
   37    * This class generates a secret key for use with the HMAC-MD5 algorithm.
   38    *
   39    * @author Jan Luehe
   40    *
   41    */
   42   
   43   public final class HmacMD5KeyGenerator extends KeyGeneratorSpi {
   44   
   45       private SecureRandom random = null;
   46       private int keysize = 64; // default keysize (in number of bytes)
   47   
   48       /**
   49        * Empty constructor
   50        */
   51       public HmacMD5KeyGenerator() {
   52       }
   53   
   54       /**
   55        * Initializes this key generator.
   56        *
   57        * @param random the source of randomness for this generator
   58        */
   59       protected void engineInit(SecureRandom random) {
   60           this.random = random;
   61       }
   62   
   63       /**
   64        * Initializes this key generator with the specified parameter
   65        * set and a user-provided source of randomness.
   66        *
   67        * @param params the key generation parameters
   68        * @param random the source of randomness for this key generator
   69        *
   70        * @exception InvalidAlgorithmParameterException if <code>params</code> is
   71        * inappropriate for this key generator
   72        */
   73       protected void engineInit(AlgorithmParameterSpec params,
   74                                 SecureRandom random)
   75           throws InvalidAlgorithmParameterException
   76       {
   77           throw new InvalidAlgorithmParameterException
   78               ("HMAC-MD5 key generation does not take any parameters");
   79       }
   80   
   81       /**
   82        * Initializes this key generator for a certain keysize, using the given
   83        * source of randomness.
   84        *
   85        * @param keysize the keysize. This is an algorithm-specific
   86        * metric specified in number of bits.
   87        * @param random the source of randomness for this key generator
   88        */
   89       protected void engineInit(int keysize, SecureRandom random) {
   90           this.keysize = (keysize+7) / 8;
   91           this.engineInit(random);
   92       }
   93   
   94       /**
   95        * Generates an HMAC-MD5 key.
   96        *
   97        * @return the new HMAC-MD5 key
   98        */
   99       protected SecretKey engineGenerateKey() {
  100           if (this.random == null) {
  101               this.random = SunJCE.RANDOM;
  102           }
  103   
  104           byte[] keyBytes = new byte[this.keysize];
  105           this.random.nextBytes(keyBytes);
  106   
  107           return new SecretKeySpec(keyBytes, "HmacMD5");
  108       }
  109   }

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