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    1   /*
    2    * Copyright (c) 1997, 2007, 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.InvalidKeyException;
   29   
   30   /**
   31    * This class represents ciphers in Plaintext Cipher Block Chaining (PCBC)
   32    * mode.
   33    *
   34    * <p>This mode is implemented independently of a particular cipher.
   35    * Ciphers to which this mode should apply (e.g., DES) must be
   36    * <i>plugged-in</i> using the constructor.
   37    *
   38    * <p>NOTE: This class does not deal with buffering or padding.
   39    *
   40    * @author Gigi Ankeny
   41    */
   42   
   43   final class PCBC extends FeedbackCipher {
   44   
   45       /*
   46        * output buffer
   47        */
   48       private final byte[] k;
   49   
   50       // variables for save/restore calls
   51       private byte[] kSave = null;
   52   
   53       PCBC(SymmetricCipher embeddedCipher) {
   54           super(embeddedCipher);
   55           k = new byte[blockSize];
   56       }
   57   
   58       /**
   59        * Gets the name of this feedback mode.
   60        *
   61        * @return the string <code>PCBC</code>
   62        */
   63       String getFeedback() {
   64           return "PCBC";
   65       }
   66   
   67       /**
   68        * Initializes the cipher in the specified mode with the given key
   69        * and iv.
   70        *
   71        * @param decrypting flag indicating encryption or decryption
   72        * @param algorithm the algorithm name
   73        * @param key the key
   74        * @param iv the iv
   75        *
   76        * @exception InvalidKeyException if the given key is inappropriate for
   77        * initializing this cipher
   78        */
   79       void init(boolean decrypting, String algorithm, byte[] key, byte[] iv)
   80               throws InvalidKeyException {
   81           if ((key == null) || (iv == null) || (iv.length != blockSize)) {
   82               throw new InvalidKeyException("Internal error");
   83           }
   84           this.iv = iv;
   85           reset();
   86           embeddedCipher.init(decrypting, algorithm, key);
   87       }
   88   
   89       /**
   90        * Resets the iv to its original value.
   91        * This is used when doFinal is called in the Cipher class, so that the
   92        * cipher can be reused (with its original iv).
   93        */
   94       void reset() {
   95           System.arraycopy(iv, 0, k, 0, blockSize);
   96       }
   97   
   98       /**
   99        * Save the current content of this cipher.
  100        */
  101       void save() {
  102           if (kSave == null) {
  103               kSave = new byte[blockSize];
  104           }
  105           System.arraycopy(k, 0, kSave, 0, blockSize);
  106   
  107       }
  108   
  109       /**
  110        * Restores the content of this cipher to the previous saved one.
  111        */
  112       void restore() {
  113           System.arraycopy(kSave, 0, k, 0, blockSize);
  114       }
  115   
  116       /**
  117        * Performs encryption operation.
  118        *
  119        * <p>The input plain text <code>plain</code>, starting at
  120        * <code>plainOffset</code> and ending at
  121        * <code>(plainOffset + len - 1)</code>, is encrypted.
  122        * The result is stored in <code>cipher</code>, starting at
  123        * <code>cipherOffset</code>.
  124        *
  125        * <p>It is the application's responsibility to make sure that
  126        * <code>plainLen</code> is a multiple of the embedded cipher's block size,
  127        * as any excess bytes are ignored.
  128        *
  129        * <p>It is also the application's responsibility to make sure that
  130        * <code>init</code> has been called before this method is called.
  131        * (This check is omitted here, to avoid double checking.)
  132        *
  133        * @param plain the buffer with the input data to be encrypted
  134        * @param plainOffset the offset in <code>plain</code>
  135        * @param plainLen the length of the input data
  136        * @param cipher the buffer for the result
  137        * @param cipherOffset the offset in <code>cipher</code>
  138        */
  139       void encrypt(byte[] plain, int plainOffset, int plainLen,
  140                           byte[] cipher, int cipherOffset)
  141       {
  142           int i;
  143           int endIndex = plainOffset + plainLen;
  144   
  145           for (; plainOffset < endIndex;
  146                plainOffset += blockSize, cipherOffset += blockSize) {
  147               for (i=0; i<blockSize; i++) {
  148                   k[i] ^= (byte)(plain[i+plainOffset]);
  149               }
  150               embeddedCipher.encryptBlock(k, 0, cipher, cipherOffset);
  151               for (i = 0; i < blockSize; i++) {
  152                   k[i] = (byte)(plain[i+plainOffset] ^ cipher[i+cipherOffset]);
  153               }
  154           }
  155       }
  156   
  157       /**
  158        * Performs decryption operation.
  159        *
  160        * <p>The input cipher text <code>cipher</code>, starting at
  161        * <code>cipherOffset</code> and ending at
  162        * <code>(cipherOffset + len - 1)</code>, is decrypted.
  163        * The result is stored in <code>plain</code>, starting at
  164        * <code>plainOffset</code>.
  165        *
  166        * <p>It is the application's responsibility to make sure that
  167        * <code>cipherLen</code> is a multiple of the embedded cipher's block
  168        * size, as any excess bytes are ignored.
  169        *
  170        * <p>It is also the application's responsibility to make sure that
  171        * <code>init</code> has been called before this method is called.
  172        * (This check is omitted here, to avoid double checking.)
  173        *
  174        * @param cipher the buffer with the input data to be decrypted
  175        * @param cipherOffset the offset in <code>cipherOffset</code>
  176        * @param cipherLen the length of the input data
  177        * @param plain the buffer for the result
  178        * @param plainOffset the offset in <code>plain</code>
  179        */
  180       void decrypt(byte[] cipher, int cipherOffset, int cipherLen,
  181                           byte[] plain, int plainOffset)
  182       {
  183           int i;
  184           int endIndex = cipherOffset + cipherLen;
  185   
  186           for (; cipherOffset < endIndex;
  187                plainOffset += blockSize, cipherOffset += blockSize) {
  188               embeddedCipher.decryptBlock(cipher, cipherOffset,
  189                                      plain, plainOffset);
  190               for (i = 0; i < blockSize; i++) {
  191                   plain[i+plainOffset] ^= k[i];
  192               }
  193               for (i = 0; i < blockSize; i++) {
  194                   k[i] = (byte)(plain[i+plainOffset] ^ cipher[i+cipherOffset]);
  195               }
  196           }
  197       }
  198   }

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