/* * Copyright (c) 1997, 2007, Oracle and/or its affiliates. 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. Oracle designates this * particular file as subject to the "Classpath" exception as provided * by Oracle 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 Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. */ package com.sun.crypto.provider; import java.security.InvalidKeyException; /** * This class represents ciphers in cipher-feedback (CFB) mode. * *
This mode is implemented independently of a particular cipher. * Ciphers to which this mode should apply (e.g., DES) must be * plugged-in using the constructor. * *
NOTE: This class does not deal with buffering or padding.
*
* @author Gigi Ankeny
*/
final class CipherFeedback extends FeedbackCipher {
/*
* encrypt/decrypt output buffer
*/
private final byte[] k;
/*
* register value, initialized with iv
*/
private final byte[] register;
/*
* number of bytes for each stream unit, defaults to the blocksize
* of the embedded cipher
*/
private int numBytes;
// variables for save/restore calls
private byte[] registerSave = null;
CipherFeedback(SymmetricCipher embeddedCipher, int numBytes) {
super(embeddedCipher);
if (numBytes > blockSize) {
numBytes = blockSize;
}
this.numBytes = numBytes;
k = new byte[blockSize];
register = new byte[blockSize];
}
/**
* Gets the name of this feedback mode.
*
* @return the string CFB
*/
String getFeedback() {
return "CFB";
}
/**
* 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();
// always encrypt mode for embedded cipher
embeddedCipher.init(false, 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, register, 0, blockSize);
}
/**
* Save the current content of this cipher.
*/
void save() {
if (registerSave == null) {
registerSave = new byte[blockSize];
}
System.arraycopy(register, 0, registerSave, 0, blockSize);
}
/**
* Restores the content of this cipher to the previous saved one.
*/
void restore() {
System.arraycopy(registerSave, 0, register, 0, blockSize);
}
/**
* Performs encryption operation.
*
*
The input plain text plain
, starting at
* plainOffset
and ending at
* (plainOffset + len - 1)
, is encrypted.
* The result is stored in cipher
, starting at
* cipherOffset
.
*
*
It is the application's responsibility to make sure that
* plainLen
is a multiple of the stream unit size
* numBytes
, as any excess bytes are ignored.
*
*
It is also the application's responsibility to make sure that
* It is the application's responsibility to make sure that
* It is also the application's responsibility to make sure that
* init
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 plain
* @param plainLen the length of the input data
* @param cipher the buffer for the result
* @param cipherOffset the offset in cipher
*/
void encrypt(byte[] plain, int plainOffset, int plainLen,
byte[] cipher, int cipherOffset)
{
int i, len;
len = blockSize - numBytes;
int loopCount = plainLen / numBytes;
int oddBytes = plainLen % numBytes;
if (len == 0) {
for (; loopCount > 0 ;
plainOffset += numBytes, cipherOffset += numBytes,
loopCount--) {
embeddedCipher.encryptBlock(register, 0, k, 0);
for (i = 0; i < blockSize; i++)
register[i] = cipher[i+cipherOffset] =
(byte)(k[i] ^ plain[i+plainOffset]);
}
if (oddBytes > 0) {
embeddedCipher.encryptBlock(register, 0, k, 0);
for (i=0; icipher
, starting at
* cipherOffset
and ending at
* (cipherOffset + len - 1)
, is decrypted.
* The result is stored in plain
, starting at
* plainOffset
.
*
* cipherLen
is a multiple of the stream unit size
* numBytes
, as any excess bytes are ignored.
*
* init
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 cipherOffset
* @param cipherLen the length of the input data
* @param plain the buffer for the result
* @param plainOffset the offset in plain
*/
void decrypt(byte[] cipher, int cipherOffset, int cipherLen,
byte[] plain, int plainOffset)
{
int i, len;
len = blockSize - numBytes;
int loopCount = cipherLen / numBytes;
int oddBytes = cipherLen % numBytes;
if (len == 0) {
for (; loopCount > 0;
plainOffset += numBytes, cipherOffset += numBytes,
loopCount--) {
embeddedCipher.encryptBlock(register, 0, k, 0);
for (i = 0; i < blockSize; i++) {
register[i] = cipher[i+cipherOffset];
plain[i+plainOffset]
= (byte)(cipher[i+cipherOffset] ^ k[i]);
}
}
if (oddBytes > 0) {
embeddedCipher.encryptBlock(register, 0, k, 0);
for (i=0; i