/*
* Copyright 1997-2007 Sun Microsystems, Inc. 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. Sun designates this
* particular file as subject to the "Classpath" exception as provided
* by Sun in the LICENSE file that accompanied this code.
*
* 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
* CA 95054 USA or visit www.sun.com if you need additional information or
* have any questions.
*/
package com.sun.crypto.provider;
import java.security.InvalidKeyException;
/**
* This class represents ciphers in Plaintext Cipher Block Chaining (PCBC)
* mode.
*
* <p>This mode is implemented independently of a particular cipher.
* Ciphers to which this mode should apply (e.g., DES) must be
* <i>plugged-in</i> using the constructor.
*
* <p>NOTE: This class does not deal with buffering or padding.
*
* @author Gigi Ankeny
*/
final class PCBC extends FeedbackCipher {
/*
* output buffer
*/
private final byte[] k;
// variables for save/restore calls
private byte[] kSave = null;
PCBC(SymmetricCipher embeddedCipher) {
super(embeddedCipher);
k = new byte[blockSize];
}
/**
* Gets the name of this feedback mode.
*
* @return the string <code>PCBC</code>
*/
String getFeedback() {
return "PCBC";
}
/**
* Initializes the cipher in the specified mode with the given key
* and iv.
*
* @param decrypting flag indicating encryption or decryption
* @param algorithm the algorithm name
* @param key the key
* @param iv the iv
*
* @exception InvalidKeyException if the given key is inappropriate for
* initializing this cipher
*/
void init(boolean decrypting, String algorithm, byte[] key, byte[] iv)
throws InvalidKeyException {
if ((key == null) || (iv == null) || (iv.length != blockSize)) {
throw new InvalidKeyException("Internal error");
}
this.iv = iv;
reset();
embeddedCipher.init(decrypting, algorithm, key);
}
/**
* Resets the iv to its original value.
* This is used when doFinal is called in the Cipher class, so that the
* cipher can be reused (with its original iv).
*/
void reset() {
System.arraycopy(iv, 0, k, 0, blockSize);
}
/**
* Save the current content of this cipher.
*/
void save() {
if (kSave == null) {
kSave = new byte[blockSize];
}
System.arraycopy(k, 0, kSave, 0, blockSize);
}
/**
* Restores the content of this cipher to the previous saved one.
*/
void restore() {
System.arraycopy(kSave, 0, k, 0, blockSize);
}
/**
* Performs encryption operation.
*
* <p>The input plain text <code>plain</code>, starting at
* <code>plainOffset</code> and ending at
* <code>(plainOffset + len - 1)</code>, is encrypted.
* The result is stored in <code>cipher</code>, starting at
* <code>cipherOffset</code>.
*
* <p>It is the application's responsibility to make sure that
* <code>plainLen</code> is a multiple of the embedded cipher's block size,
* as any excess bytes are ignored.
*
* <p>It is also the application's responsibility to make sure that
* <code>init</code> has been called before this method is called.
* (This check is omitted here, to avoid double checking.)
*
* @param plain the buffer with the input data to be encrypted
* @param plainOffset the offset in <code>plain</code>
* @param plainLen the length of the input data
* @param cipher the buffer for the result
* @param cipherOffset the offset in <code>cipher</code>
*/
void encrypt(byte[] plain, int plainOffset, int plainLen,
byte[] cipher, int cipherOffset)
{
int i;
int endIndex = plainOffset + plainLen;
for (; plainOffset < endIndex;
plainOffset += blockSize, cipherOffset += blockSize) {
for (i=0; i<blockSize; i++) {
k[i] ^= (byte)(plain[i+plainOffset]);
}
embeddedCipher.encryptBlock(k, 0, cipher, cipherOffset);
for (i = 0; i < blockSize; i++) {
k[i] = (byte)(plain[i+plainOffset] ^ cipher[i+cipherOffset]);
}
}
}
/**
* Performs decryption operation.
*
* <p>The input cipher text <code>cipher</code>, starting at
* <code>cipherOffset</code> and ending at
* <code>(cipherOffset + len - 1)</code>, is decrypted.
* The result is stored in <code>plain</code>, starting at
* <code>plainOffset</code>.
*
* <p>It is the application's responsibility to make sure that
* <code>cipherLen</code> is a multiple of the embedded cipher's block
* size, as any excess bytes are ignored.
*
* <p>It is also the application's responsibility to make sure that
* <code>init</code> has been called before this method is called.
* (This check is omitted here, to avoid double checking.)
*
* @param cipher the buffer with the input data to be decrypted
* @param cipherOffset the offset in <code>cipherOffset</code>
* @param cipherLen the length of the input data
* @param plain the buffer for the result
* @param plainOffset the offset in <code>plain</code>
*/
void decrypt(byte[] cipher, int cipherOffset, int cipherLen,
byte[] plain, int plainOffset)
{
int i;
int endIndex = cipherOffset + cipherLen;
for (; cipherOffset < endIndex;
plainOffset += blockSize, cipherOffset += blockSize) {
embeddedCipher.decryptBlock(cipher, cipherOffset,
plain, plainOffset);
for (i = 0; i < blockSize; i++) {
plain[i+plainOffset] ^= k[i];
}
for (i = 0; i < blockSize; i++) {
k[i] = (byte)(plain[i+plainOffset] ^ cipher[i+cipherOffset]);
}
}
}
}