<?php
namespace Kant\Secure\Crypt;

/* vim: set expandtab tabstop=4 shiftwidth=4 softtabstop=4: */

/**
 * Pure-PHP implementation of DES.
 *
 * Uses mcrypt, if available, and an internal implementation, otherwise.
 *
 * PHP versions 4 and 5
 *
 * Useful resources are as follows:
 *
 * - {@link http://en.wikipedia.org/wiki/DES_supplementary_material Wikipedia: DES supplementary material}
 * - {@link http://www.itl.nist.gov/fipspubs/fip46-2.htm FIPS 46-2 - (DES), Data Encryption Standard}
 * - {@link http://www.cs.eku.edu/faculty/styer/460/Encrypt/JS-DES.html JavaScript DES Example}
 *
 * Here's a short example of how to use this library:
 * <code>
 * <?php
 * include('Crypt/DES.php');
 *
 * $des = new Crypt_DES();
 *
 * $des->setKey('abcdefgh');
 *
 * $size = 10 * 1024;
 * $plaintext = '';
 * for ($i = 0; $i < $size; $i++) {
 * $plaintext.= 'a';
 * }
 *
 * echo $des->decrypt($des->encrypt($plaintext));
 * ?>
 * </code>
 *
 * LICENSE: Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 *
 * @category Crypt
 * @package Crypt_DES
 * @author Jim Wigginton <terrafrost@php.net>
 * @copyright MMVII Jim Wigginton
 * @license http://www.opensource.org/licenses/mit-license.html MIT License
 * @version $Id: DES.php,v 1.12 2010/02/09 06:10:26 terrafrost Exp $
 * @link http://phpseclib.sourceforge.net
 */
/*
 * #@+
 * @access private
 * @see Crypt_DES::_prepareKey()
 * @see Crypt_DES::_processBlock()
 */
/**
 * Contains array_reverse($keys[CRYPT_DES_DECRYPT])
 */
define('CRYPT_DES_ENCRYPT', 0);
/**
 * Contains array_reverse($keys[CRYPT_DES_ENCRYPT])
 */
define('CRYPT_DES_DECRYPT', 1);
/**
 * Contains $keys[CRYPT_DES_ENCRYPT] as 1-dim array
 */
define('CRYPT_DES_ENCRYPT_1DIM', 2);
/**
 * Contains $keys[CRYPT_DES_DECRYPT] as 1-dim array
 */
define('CRYPT_DES_DECRYPT_1DIM', 3);
/* * #@- */

/*
 * #@+
 * @access public
 * @see Crypt_DES::encrypt()
 * @see Crypt_DES::decrypt()
 */
/**
 * Encrypt / decrypt using the Counter mode.
 *
 * Set to -1 since that's what Crypt/Random.php uses to index the CTR mode.
 *
 * @link http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation#Counter_.28CTR.29
 */
define('CRYPT_DES_MODE_CTR', - 1);
/**
 * Encrypt / decrypt using the Electronic Code Book mode.
 *
 * @link http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation#Electronic_codebook_.28ECB.29
 */
define('CRYPT_DES_MODE_ECB', 1);
/**
 * Encrypt / decrypt using the Code Book Chaining mode.
 *
 * @link http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation#Cipher-block_chaining_.28CBC.29
 */
define('CRYPT_DES_MODE_CBC', 2);
/**
 * Encrypt / decrypt using the Cipher Feedback mode.
 *
 * @link http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation#Cipher_feedback_.28CFB.29
 */
define('CRYPT_DES_MODE_CFB', 3);
/**
 * Encrypt / decrypt using the Cipher Feedback mode.
 *
 * @link http://en.wikipedia.org/wiki/Block_cipher_modes_of_operation#Output_feedback_.28OFB.29
 */
define('CRYPT_DES_MODE_OFB', 4);
/* * #@- */

/*
 * #@+
 * @access private
 * @see Crypt_DES::Crypt_DES()
 */
/**
 * Toggles the internal implementation
 */
define('CRYPT_DES_MODE_INTERNAL', 1);
/**
 * Toggles the mcrypt implementation
 */
define('CRYPT_DES_MODE_MCRYPT', 2);

/* * #@- */

/**
 * Pure-PHP implementation of DES.
 *
 * @author Jim Wigginton <terrafrost@php.net>
 * @version 0.1.0
 * @access public
 * @package Crypt_DES
 */
class Crypt_DES
{

    /**
     * The Key Schedule
     *
     * @see Crypt_DES::setKey()
     * @var Array
     * @access private
     */
    var $keys = "\0\0\0\0\0\0\0\0";

    /**
     * The Encryption Mode
     *
     * @see Crypt_DES::Crypt_DES()
     * @var Integer
     * @access private
     */
    var $mode;

    /**
     * Continuous Buffer status
     *
     * @see Crypt_DES::enableContinuousBuffer()
     * @var Boolean
     * @access private
     */
    var $continuousBuffer = false;

    /**
     * Padding status
     *
     * @see Crypt_DES::enablePadding()
     * @var Boolean
     * @access private
     */
    var $padding = true;

    /**
     * The Initialization Vector
     *
     * @see Crypt_DES::setIV()
     * @var String
     * @access private
     */
    var $iv = "\0\0\0\0\0\0\0\0";

    /**
     * A "sliding" Initialization Vector
     *
     * @see Crypt_DES::enableContinuousBuffer()
     * @var String
     * @access private
     */
    var $encryptIV = "\0\0\0\0\0\0\0\0";

    /**
     * A "sliding" Initialization Vector
     *
     * @see Crypt_DES::enableContinuousBuffer()
     * @var String
     * @access private
     */
    var $decryptIV = "\0\0\0\0\0\0\0\0";

    /**
     * mcrypt resource for encryption
     *
     * The mcrypt resource can be recreated every time something needs to be created or it can be created just once.
     * Since mcrypt operates in continuous mode, by default, it'll need to be recreated when in non-continuous mode.
     *
     * @see Crypt_DES::encrypt()
     * @var String
     * @access private
     */
    var $enmcrypt;

    /**
     * mcrypt resource for decryption
     *
     * The mcrypt resource can be recreated every time something needs to be created or it can be created just once.
     * Since mcrypt operates in continuous mode, by default, it'll need to be recreated when in non-continuous mode.
     *
     * @see Crypt_DES::decrypt()
     * @var String
     * @access private
     */
    var $demcrypt;

    /**
     * Does the enmcrypt resource need to be (re)initialized?
     *
     * @see Crypt_DES::setKey()
     * @see Crypt_DES::setIV()
     * @var Boolean
     * @access private
     */
    var $enchanged = true;

    /**
     * Does the demcrypt resource need to be (re)initialized?
     *
     * @see Crypt_DES::setKey()
     * @see Crypt_DES::setIV()
     * @var Boolean
     * @access private
     */
    var $dechanged = true;

    /**
     * Is the mode one that is paddable?
     *
     * @see Crypt_DES::Crypt_DES()
     * @var Boolean
     * @access private
     */
    var $paddable = false;

    /**
     * Encryption buffer for CTR, OFB and CFB modes
     *
     * @see Crypt_DES::encrypt()
     * @var Array
     * @access private
     */
    var $enbuffer = array(
        'encrypted' => '',
        'xor' => '',
        'pos' => 0,
        'enmcrypt_init' => true
    );

    /**
     * Decryption buffer for CTR, OFB and CFB modes
     *
     * @see Crypt_DES::decrypt()
     * @var Array
     * @access private
     */
    var $debuffer = array(
        'ciphertext' => '',
        'xor' => '',
        'pos' => 0,
        'demcrypt_init' => true
    );

    /**
     * mcrypt resource for CFB mode
     *
     * @see Crypt_DES::encrypt()
     * @see Crypt_DES::decrypt()
     * @var String
     * @access private
     */
    var $ecb;

    /**
     * Performance-optimized callback function for en/decrypt()
     *
     * @var Callback
     * @access private
     */
    var $inline_crypt;

    /**
     * Holds whether performance-optimized $inline_crypt should be used or not.
     *
     * @var Boolean
     * @access private
     */
    var $use_inline_crypt = false;

    /**
     * Shuffle table.
     *
     * For each byte value index, the entry holds an 8-byte string
     * with each byte containing all bits in the same state as the
     * corresponding bit in the index value.
     *
     * @see Crypt_DES::_processBlock()
     * @see Crypt_DES::_prepareKey()
     * @var Array
     * @access private
     */
    var $shuffle = array(
        "\x00\x00\x00\x00\x00\x00\x00\x00",
        "\x00\x00\x00\x00\x00\x00\x00\xFF",
        "\x00\x00\x00\x00\x00\x00\xFF\x00",
        "\x00\x00\x00\x00\x00\x00\xFF\xFF",
        "\x00\x00\x00\x00\x00\xFF\x00\x00",
        "\x00\x00\x00\x00\x00\xFF\x00\xFF",
        "\x00\x00\x00\x00\x00\xFF\xFF\x00",
        "\x00\x00\x00\x00\x00\xFF\xFF\xFF",
        "\x00\x00\x00\x00\xFF\x00\x00\x00",
        "\x00\x00\x00\x00\xFF\x00\x00\xFF",
        "\x00\x00\x00\x00\xFF\x00\xFF\x00",
        "\x00\x00\x00\x00\xFF\x00\xFF\xFF",
        "\x00\x00\x00\x00\xFF\xFF\x00\x00",
        "\x00\x00\x00\x00\xFF\xFF\x00\xFF",
        "\x00\x00\x00\x00\xFF\xFF\xFF\x00",
        "\x00\x00\x00\x00\xFF\xFF\xFF\xFF",
        "\x00\x00\x00\xFF\x00\x00\x00\x00",
        "\x00\x00\x00\xFF\x00\x00\x00\xFF",
        "\x00\x00\x00\xFF\x00\x00\xFF\x00",
        "\x00\x00\x00\xFF\x00\x00\xFF\xFF",
        "\x00\x00\x00\xFF\x00\xFF\x00\x00",
        "\x00\x00\x00\xFF\x00\xFF\x00\xFF",
        "\x00\x00\x00\xFF\x00\xFF\xFF\x00",
        "\x00\x00\x00\xFF\x00\xFF\xFF\xFF",
        "\x00\x00\x00\xFF\xFF\x00\x00\x00",
        "\x00\x00\x00\xFF\xFF\x00\x00\xFF",
        "\x00\x00\x00\xFF\xFF\x00\xFF\x00",
        "\x00\x00\x00\xFF\xFF\x00\xFF\xFF",
        "\x00\x00\x00\xFF\xFF\xFF\x00\x00",
        "\x00\x00\x00\xFF\xFF\xFF\x00\xFF",
        "\x00\x00\x00\xFF\xFF\xFF\xFF\x00",
        "\x00\x00\x00\xFF\xFF\xFF\xFF\xFF",
        "\x00\x00\xFF\x00\x00\x00\x00\x00",
        "\x00\x00\xFF\x00\x00\x00\x00\xFF",
        "\x00\x00\xFF\x00\x00\x00\xFF\x00",
        "\x00\x00\xFF\x00\x00\x00\xFF\xFF",
        "\x00\x00\xFF\x00\x00\xFF\x00\x00",
        "\x00\x00\xFF\x00\x00\xFF\x00\xFF",
        "\x00\x00\xFF\x00\x00\xFF\xFF\x00",
        "\x00\x00\xFF\x00\x00\xFF\xFF\xFF",
        "\x00\x00\xFF\x00\xFF\x00\x00\x00",
        "\x00\x00\xFF\x00\xFF\x00\x00\xFF",
        "\x00\x00\xFF\x00\xFF\x00\xFF\x00",
        "\x00\x00\xFF\x00\xFF\x00\xFF\xFF",
        "\x00\x00\xFF\x00\xFF\xFF\x00\x00",
        "\x00\x00\xFF\x00\xFF\xFF\x00\xFF",
        "\x00\x00\xFF\x00\xFF\xFF\xFF\x00",
        "\x00\x00\xFF\x00\xFF\xFF\xFF\xFF",
        "\x00\x00\xFF\xFF\x00\x00\x00\x00",
        "\x00\x00\xFF\xFF\x00\x00\x00\xFF",
        "\x00\x00\xFF\xFF\x00\x00\xFF\x00",
        "\x00\x00\xFF\xFF\x00\x00\xFF\xFF",
        "\x00\x00\xFF\xFF\x00\xFF\x00\x00",
        "\x00\x00\xFF\xFF\x00\xFF\x00\xFF",
        "\x00\x00\xFF\xFF\x00\xFF\xFF\x00",
        "\x00\x00\xFF\xFF\x00\xFF\xFF\xFF",
        "\x00\x00\xFF\xFF\xFF\x00\x00\x00",
        "\x00\x00\xFF\xFF\xFF\x00\x00\xFF",
        "\x00\x00\xFF\xFF\xFF\x00\xFF\x00",
        "\x00\x00\xFF\xFF\xFF\x00\xFF\xFF",
        "\x00\x00\xFF\xFF\xFF\xFF\x00\x00",
        "\x00\x00\xFF\xFF\xFF\xFF\x00\xFF",
        "\x00\x00\xFF\xFF\xFF\xFF\xFF\x00",
        "\x00\x00\xFF\xFF\xFF\xFF\xFF\xFF",
        "\x00\xFF\x00\x00\x00\x00\x00\x00",
        "\x00\xFF\x00\x00\x00\x00\x00\xFF",
        "\x00\xFF\x00\x00\x00\x00\xFF\x00",
        "\x00\xFF\x00\x00\x00\x00\xFF\xFF",
        "\x00\xFF\x00\x00\x00\xFF\x00\x00",
        "\x00\xFF\x00\x00\x00\xFF\x00\xFF",
        "\x00\xFF\x00\x00\x00\xFF\xFF\x00",
        "\x00\xFF\x00\x00\x00\xFF\xFF\xFF",
        "\x00\xFF\x00\x00\xFF\x00\x00\x00",
        "\x00\xFF\x00\x00\xFF\x00\x00\xFF",
        "\x00\xFF\x00\x00\xFF\x00\xFF\x00",
        "\x00\xFF\x00\x00\xFF\x00\xFF\xFF",
        "\x00\xFF\x00\x00\xFF\xFF\x00\x00",
        "\x00\xFF\x00\x00\xFF\xFF\x00\xFF",
        "\x00\xFF\x00\x00\xFF\xFF\xFF\x00",
        "\x00\xFF\x00\x00\xFF\xFF\xFF\xFF",
        "\x00\xFF\x00\xFF\x00\x00\x00\x00",
        "\x00\xFF\x00\xFF\x00\x00\x00\xFF",
        "\x00\xFF\x00\xFF\x00\x00\xFF\x00",
        "\x00\xFF\x00\xFF\x00\x00\xFF\xFF",
        "\x00\xFF\x00\xFF\x00\xFF\x00\x00",
        "\x00\xFF\x00\xFF\x00\xFF\x00\xFF",
        "\x00\xFF\x00\xFF\x00\xFF\xFF\x00",
        "\x00\xFF\x00\xFF\x00\xFF\xFF\xFF",
        "\x00\xFF\x00\xFF\xFF\x00\x00\x00",
        "\x00\xFF\x00\xFF\xFF\x00\x00\xFF",
        "\x00\xFF\x00\xFF\xFF\x00\xFF\x00",
        "\x00\xFF\x00\xFF\xFF\x00\xFF\xFF",
        "\x00\xFF\x00\xFF\xFF\xFF\x00\x00",
        "\x00\xFF\x00\xFF\xFF\xFF\x00\xFF",
        "\x00\xFF\x00\xFF\xFF\xFF\xFF\x00",
        "\x00\xFF\x00\xFF\xFF\xFF\xFF\xFF",
        "\x00\xFF\xFF\x00\x00\x00\x00\x00",
        "\x00\xFF\xFF\x00\x00\x00\x00\xFF",
        "\x00\xFF\xFF\x00\x00\x00\xFF\x00",
        "\x00\xFF\xFF\x00\x00\x00\xFF\xFF",
        "\x00\xFF\xFF\x00\x00\xFF\x00\x00",
        "\x00\xFF\xFF\x00\x00\xFF\x00\xFF",
        "\x00\xFF\xFF\x00\x00\xFF\xFF\x00",
        "\x00\xFF\xFF\x00\x00\xFF\xFF\xFF",
        "\x00\xFF\xFF\x00\xFF\x00\x00\x00",
        "\x00\xFF\xFF\x00\xFF\x00\x00\xFF",
        "\x00\xFF\xFF\x00\xFF\x00\xFF\x00",
        "\x00\xFF\xFF\x00\xFF\x00\xFF\xFF",
        "\x00\xFF\xFF\x00\xFF\xFF\x00\x00",
        "\x00\xFF\xFF\x00\xFF\xFF\x00\xFF",
        "\x00\xFF\xFF\x00\xFF\xFF\xFF\x00",
        "\x00\xFF\xFF\x00\xFF\xFF\xFF\xFF",
        "\x00\xFF\xFF\xFF\x00\x00\x00\x00",
        "\x00\xFF\xFF\xFF\x00\x00\x00\xFF",
        "\x00\xFF\xFF\xFF\x00\x00\xFF\x00",
        "\x00\xFF\xFF\xFF\x00\x00\xFF\xFF",
        "\x00\xFF\xFF\xFF\x00\xFF\x00\x00",
        "\x00\xFF\xFF\xFF\x00\xFF\x00\xFF",
        "\x00\xFF\xFF\xFF\x00\xFF\xFF\x00",
        "\x00\xFF\xFF\xFF\x00\xFF\xFF\xFF",
        "\x00\xFF\xFF\xFF\xFF\x00\x00\x00",
        "\x00\xFF\xFF\xFF\xFF\x00\x00\xFF",
        "\x00\xFF\xFF\xFF\xFF\x00\xFF\x00",
        "\x00\xFF\xFF\xFF\xFF\x00\xFF\xFF",
        "\x00\xFF\xFF\xFF\xFF\xFF\x00\x00",
        "\x00\xFF\xFF\xFF\xFF\xFF\x00\xFF",
        "\x00\xFF\xFF\xFF\xFF\xFF\xFF\x00",
        "\x00\xFF\xFF\xFF\xFF\xFF\xFF\xFF",
        "\xFF\x00\x00\x00\x00\x00\x00\x00",
        "\xFF\x00\x00\x00\x00\x00\x00\xFF",
        "\xFF\x00\x00\x00\x00\x00\xFF\x00",
        "\xFF\x00\x00\x00\x00\x00\xFF\xFF",
        "\xFF\x00\x00\x00\x00\xFF\x00\x00",
        "\xFF\x00\x00\x00\x00\xFF\x00\xFF",
        "\xFF\x00\x00\x00\x00\xFF\xFF\x00",
        "\xFF\x00\x00\x00\x00\xFF\xFF\xFF",
        "\xFF\x00\x00\x00\xFF\x00\x00\x00",
        "\xFF\x00\x00\x00\xFF\x00\x00\xFF",
        "\xFF\x00\x00\x00\xFF\x00\xFF\x00",
        "\xFF\x00\x00\x00\xFF\x00\xFF\xFF",
        "\xFF\x00\x00\x00\xFF\xFF\x00\x00",
        "\xFF\x00\x00\x00\xFF\xFF\x00\xFF",
        "\xFF\x00\x00\x00\xFF\xFF\xFF\x00",
        "\xFF\x00\x00\x00\xFF\xFF\xFF\xFF",
        "\xFF\x00\x00\xFF\x00\x00\x00\x00",
        "\xFF\x00\x00\xFF\x00\x00\x00\xFF",
        "\xFF\x00\x00\xFF\x00\x00\xFF\x00",
        "\xFF\x00\x00\xFF\x00\x00\xFF\xFF",
        "\xFF\x00\x00\xFF\x00\xFF\x00\x00",
        "\xFF\x00\x00\xFF\x00\xFF\x00\xFF",
        "\xFF\x00\x00\xFF\x00\xFF\xFF\x00",
        "\xFF\x00\x00\xFF\x00\xFF\xFF\xFF",
        "\xFF\x00\x00\xFF\xFF\x00\x00\x00",
        "\xFF\x00\x00\xFF\xFF\x00\x00\xFF",
        "\xFF\x00\x00\xFF\xFF\x00\xFF\x00",
        "\xFF\x00\x00\xFF\xFF\x00\xFF\xFF",
        "\xFF\x00\x00\xFF\xFF\xFF\x00\x00",
        "\xFF\x00\x00\xFF\xFF\xFF\x00\xFF",
        "\xFF\x00\x00\xFF\xFF\xFF\xFF\x00",
        "\xFF\x00\x00\xFF\xFF\xFF\xFF\xFF",
        "\xFF\x00\xFF\x00\x00\x00\x00\x00",
        "\xFF\x00\xFF\x00\x00\x00\x00\xFF",
        "\xFF\x00\xFF\x00\x00\x00\xFF\x00",
        "\xFF\x00\xFF\x00\x00\x00\xFF\xFF",
        "\xFF\x00\xFF\x00\x00\xFF\x00\x00",
        "\xFF\x00\xFF\x00\x00\xFF\x00\xFF",
        "\xFF\x00\xFF\x00\x00\xFF\xFF\x00",
        "\xFF\x00\xFF\x00\x00\xFF\xFF\xFF",
        "\xFF\x00\xFF\x00\xFF\x00\x00\x00",
        "\xFF\x00\xFF\x00\xFF\x00\x00\xFF",
        "\xFF\x00\xFF\x00\xFF\x00\xFF\x00",
        "\xFF\x00\xFF\x00\xFF\x00\xFF\xFF",
        "\xFF\x00\xFF\x00\xFF\xFF\x00\x00",
        "\xFF\x00\xFF\x00\xFF\xFF\x00\xFF",
        "\xFF\x00\xFF\x00\xFF\xFF\xFF\x00",
        "\xFF\x00\xFF\x00\xFF\xFF\xFF\xFF",
        "\xFF\x00\xFF\xFF\x00\x00\x00\x00",
        "\xFF\x00\xFF\xFF\x00\x00\x00\xFF",
        "\xFF\x00\xFF\xFF\x00\x00\xFF\x00",
        "\xFF\x00\xFF\xFF\x00\x00\xFF\xFF",
        "\xFF\x00\xFF\xFF\x00\xFF\x00\x00",
        "\xFF\x00\xFF\xFF\x00\xFF\x00\xFF",
        "\xFF\x00\xFF\xFF\x00\xFF\xFF\x00",
        "\xFF\x00\xFF\xFF\x00\xFF\xFF\xFF",
        "\xFF\x00\xFF\xFF\xFF\x00\x00\x00",
        "\xFF\x00\xFF\xFF\xFF\x00\x00\xFF",
        "\xFF\x00\xFF\xFF\xFF\x00\xFF\x00",
        "\xFF\x00\xFF\xFF\xFF\x00\xFF\xFF",
        "\xFF\x00\xFF\xFF\xFF\xFF\x00\x00",
        "\xFF\x00\xFF\xFF\xFF\xFF\x00\xFF",
        "\xFF\x00\xFF\xFF\xFF\xFF\xFF\x00",
        "\xFF\x00\xFF\xFF\xFF\xFF\xFF\xFF",
        "\xFF\xFF\x00\x00\x00\x00\x00\x00",
        "\xFF\xFF\x00\x00\x00\x00\x00\xFF",
        "\xFF\xFF\x00\x00\x00\x00\xFF\x00",
        "\xFF\xFF\x00\x00\x00\x00\xFF\xFF",
        "\xFF\xFF\x00\x00\x00\xFF\x00\x00",
        "\xFF\xFF\x00\x00\x00\xFF\x00\xFF",
        "\xFF\xFF\x00\x00\x00\xFF\xFF\x00",
        "\xFF\xFF\x00\x00\x00\xFF\xFF\xFF",
        "\xFF\xFF\x00\x00\xFF\x00\x00\x00",
        "\xFF\xFF\x00\x00\xFF\x00\x00\xFF",
        "\xFF\xFF\x00\x00\xFF\x00\xFF\x00",
        "\xFF\xFF\x00\x00\xFF\x00\xFF\xFF",
        "\xFF\xFF\x00\x00\xFF\xFF\x00\x00",
        "\xFF\xFF\x00\x00\xFF\xFF\x00\xFF",
        "\xFF\xFF\x00\x00\xFF\xFF\xFF\x00",
        "\xFF\xFF\x00\x00\xFF\xFF\xFF\xFF",
        "\xFF\xFF\x00\xFF\x00\x00\x00\x00",
        "\xFF\xFF\x00\xFF\x00\x00\x00\xFF",
        "\xFF\xFF\x00\xFF\x00\x00\xFF\x00",
        "\xFF\xFF\x00\xFF\x00\x00\xFF\xFF",
        "\xFF\xFF\x00\xFF\x00\xFF\x00\x00",
        "\xFF\xFF\x00\xFF\x00\xFF\x00\xFF",
        "\xFF\xFF\x00\xFF\x00\xFF\xFF\x00",
        "\xFF\xFF\x00\xFF\x00\xFF\xFF\xFF",
        "\xFF\xFF\x00\xFF\xFF\x00\x00\x00",
        "\xFF\xFF\x00\xFF\xFF\x00\x00\xFF",
        "\xFF\xFF\x00\xFF\xFF\x00\xFF\x00",
        "\xFF\xFF\x00\xFF\xFF\x00\xFF\xFF",
        "\xFF\xFF\x00\xFF\xFF\xFF\x00\x00",
        "\xFF\xFF\x00\xFF\xFF\xFF\x00\xFF",
        "\xFF\xFF\x00\xFF\xFF\xFF\xFF\x00",
        "\xFF\xFF\x00\xFF\xFF\xFF\xFF\xFF",
        "\xFF\xFF\xFF\x00\x00\x00\x00\x00",
        "\xFF\xFF\xFF\x00\x00\x00\x00\xFF",
        "\xFF\xFF\xFF\x00\x00\x00\xFF\x00",
        "\xFF\xFF\xFF\x00\x00\x00\xFF\xFF",
        "\xFF\xFF\xFF\x00\x00\xFF\x00\x00",
        "\xFF\xFF\xFF\x00\x00\xFF\x00\xFF",
        "\xFF\xFF\xFF\x00\x00\xFF\xFF\x00",
        "\xFF\xFF\xFF\x00\x00\xFF\xFF\xFF",
        "\xFF\xFF\xFF\x00\xFF\x00\x00\x00",
        "\xFF\xFF\xFF\x00\xFF\x00\x00\xFF",
        "\xFF\xFF\xFF\x00\xFF\x00\xFF\x00",
        "\xFF\xFF\xFF\x00\xFF\x00\xFF\xFF",
        "\xFF\xFF\xFF\x00\xFF\xFF\x00\x00",
        "\xFF\xFF\xFF\x00\xFF\xFF\x00\xFF",
        "\xFF\xFF\xFF\x00\xFF\xFF\xFF\x00",
        "\xFF\xFF\xFF\x00\xFF\xFF\xFF\xFF",
        "\xFF\xFF\xFF\xFF\x00\x00\x00\x00",
        "\xFF\xFF\xFF\xFF\x00\x00\x00\xFF",
        "\xFF\xFF\xFF\xFF\x00\x00\xFF\x00",
        "\xFF\xFF\xFF\xFF\x00\x00\xFF\xFF",
        "\xFF\xFF\xFF\xFF\x00\xFF\x00\x00",
        "\xFF\xFF\xFF\xFF\x00\xFF\x00\xFF",
        "\xFF\xFF\xFF\xFF\x00\xFF\xFF\x00",
        "\xFF\xFF\xFF\xFF\x00\xFF\xFF\xFF",
        "\xFF\xFF\xFF\xFF\xFF\x00\x00\x00",
        "\xFF\xFF\xFF\xFF\xFF\x00\x00\xFF",
        "\xFF\xFF\xFF\xFF\xFF\x00\xFF\x00",
        "\xFF\xFF\xFF\xFF\xFF\x00\xFF\xFF",
        "\xFF\xFF\xFF\xFF\xFF\xFF\x00\x00",
        "\xFF\xFF\xFF\xFF\xFF\xFF\x00\xFF",
        "\xFF\xFF\xFF\xFF\xFF\xFF\xFF\x00",
        "\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF"
    );

    /**
     * IP mapping helper table.
     *
     * Indexing this table with each source byte performs the initial bit permutation.
     *
     * @var Array
     * @access private
     */
    var $ipmap = array(
        0x00,
        0x10,
        0x01,
        0x11,
        0x20,
        0x30,
        0x21,
        0x31,
        0x02,
        0x12,
        0x03,
        0x13,
        0x22,
        0x32,
        0x23,
        0x33,
        0x40,
        0x50,
        0x41,
        0x51,
        0x60,
        0x70,
        0x61,
        0x71,
        0x42,
        0x52,
        0x43,
        0x53,
        0x62,
        0x72,
        0x63,
        0x73,
        0x04,
        0x14,
        0x05,
        0x15,
        0x24,
        0x34,
        0x25,
        0x35,
        0x06,
        0x16,
        0x07,
        0x17,
        0x26,
        0x36,
        0x27,
        0x37,
        0x44,
        0x54,
        0x45,
        0x55,
        0x64,
        0x74,
        0x65,
        0x75,
        0x46,
        0x56,
        0x47,
        0x57,
        0x66,
        0x76,
        0x67,
        0x77,
        0x80,
        0x90,
        0x81,
        0x91,
        0xA0,
        0xB0,
        0xA1,
        0xB1,
        0x82,
        0x92,
        0x83,
        0x93,
        0xA2,
        0xB2,
        0xA3,
        0xB3,
        0xC0,
        0xD0,
        0xC1,
        0xD1,
        0xE0,
        0xF0,
        0xE1,
        0xF1,
        0xC2,
        0xD2,
        0xC3,
        0xD3,
        0xE2,
        0xF2,
        0xE3,
        0xF3,
        0x84,
        0x94,
        0x85,
        0x95,
        0xA4,
        0xB4,
        0xA5,
        0xB5,
        0x86,
        0x96,
        0x87,
        0x97,
        0xA6,
        0xB6,
        0xA7,
        0xB7,
        0xC4,
        0xD4,
        0xC5,
        0xD5,
        0xE4,
        0xF4,
        0xE5,
        0xF5,
        0xC6,
        0xD6,
        0xC7,
        0xD7,
        0xE6,
        0xF6,
        0xE7,
        0xF7,
        0x08,
        0x18,
        0x09,
        0x19,
        0x28,
        0x38,
        0x29,
        0x39,
        0x0A,
        0x1A,
        0x0B,
        0x1B,
        0x2A,
        0x3A,
        0x2B,
        0x3B,
        0x48,
        0x58,
        0x49,
        0x59,
        0x68,
        0x78,
        0x69,
        0x79,
        0x4A,
        0x5A,
        0x4B,
        0x5B,
        0x6A,
        0x7A,
        0x6B,
        0x7B,
        0x0C,
        0x1C,
        0x0D,
        0x1D,
        0x2C,
        0x3C,
        0x2D,
        0x3D,
        0x0E,
        0x1E,
        0x0F,
        0x1F,
        0x2E,
        0x3E,
        0x2F,
        0x3F,
        0x4C,
        0x5C,
        0x4D,
        0x5D,
        0x6C,
        0x7C,
        0x6D,
        0x7D,
        0x4E,
        0x5E,
        0x4F,
        0x5F,
        0x6E,
        0x7E,
        0x6F,
        0x7F,
        0x88,
        0x98,
        0x89,
        0x99,
        0xA8,
        0xB8,
        0xA9,
        0xB9,
        0x8A,
        0x9A,
        0x8B,
        0x9B,
        0xAA,
        0xBA,
        0xAB,
        0xBB,
        0xC8,
        0xD8,
        0xC9,
        0xD9,
        0xE8,
        0xF8,
        0xE9,
        0xF9,
        0xCA,
        0xDA,
        0xCB,
        0xDB,
        0xEA,
        0xFA,
        0xEB,
        0xFB,
        0x8C,
        0x9C,
        0x8D,
        0x9D,
        0xAC,
        0xBC,
        0xAD,
        0xBD,
        0x8E,
        0x9E,
        0x8F,
        0x9F,
        0xAE,
        0xBE,
        0xAF,
        0xBF,
        0xCC,
        0xDC,
        0xCD,
        0xDD,
        0xEC,
        0xFC,
        0xED,
        0xFD,
        0xCE,
        0xDE,
        0xCF,
        0xDF,
        0xEE,
        0xFE,
        0xEF,
        0xFF
    );

    /**
     * Inverse IP mapping helper table.
     * Indexing this table with a byte value reverses the bit order.
     *
     * @var Array
     * @access private
     */
    var $invipmap = array(
        0x00,
        0x80,
        0x40,
        0xC0,
        0x20,
        0xA0,
        0x60,
        0xE0,
        0x10,
        0x90,
        0x50,
        0xD0,
        0x30,
        0xB0,
        0x70,
        0xF0,
        0x08,
        0x88,
        0x48,
        0xC8,
        0x28,
        0xA8,
        0x68,
        0xE8,
        0x18,
        0x98,
        0x58,
        0xD8,
        0x38,
        0xB8,
        0x78,
        0xF8,
        0x04,
        0x84,
        0x44,
        0xC4,
        0x24,
        0xA4,
        0x64,
        0xE4,
        0x14,
        0x94,
        0x54,
        0xD4,
        0x34,
        0xB4,
        0x74,
        0xF4,
        0x0C,
        0x8C,
        0x4C,
        0xCC,
        0x2C,
        0xAC,
        0x6C,
        0xEC,
        0x1C,
        0x9C,
        0x5C,
        0xDC,
        0x3C,
        0xBC,
        0x7C,
        0xFC,
        0x02,
        0x82,
        0x42,
        0xC2,
        0x22,
        0xA2,
        0x62,
        0xE2,
        0x12,
        0x92,
        0x52,
        0xD2,
        0x32,
        0xB2,
        0x72,
        0xF2,
        0x0A,
        0x8A,
        0x4A,
        0xCA,
        0x2A,
        0xAA,
        0x6A,
        0xEA,
        0x1A,
        0x9A,
        0x5A,
        0xDA,
        0x3A,
        0xBA,
        0x7A,
        0xFA,
        0x06,
        0x86,
        0x46,
        0xC6,
        0x26,
        0xA6,
        0x66,
        0xE6,
        0x16,
        0x96,
        0x56,
        0xD6,
        0x36,
        0xB6,
        0x76,
        0xF6,
        0x0E,
        0x8E,
        0x4E,
        0xCE,
        0x2E,
        0xAE,
        0x6E,
        0xEE,
        0x1E,
        0x9E,
        0x5E,
        0xDE,
        0x3E,
        0xBE,
        0x7E,
        0xFE,
        0x01,
        0x81,
        0x41,
        0xC1,
        0x21,
        0xA1,
        0x61,
        0xE1,
        0x11,
        0x91,
        0x51,
        0xD1,
        0x31,
        0xB1,
        0x71,
        0xF1,
        0x09,
        0x89,
        0x49,
        0xC9,
        0x29,
        0xA9,
        0x69,
        0xE9,
        0x19,
        0x99,
        0x59,
        0xD9,
        0x39,
        0xB9,
        0x79,
        0xF9,
        0x05,
        0x85,
        0x45,
        0xC5,
        0x25,
        0xA5,
        0x65,
        0xE5,
        0x15,
        0x95,
        0x55,
        0xD5,
        0x35,
        0xB5,
        0x75,
        0xF5,
        0x0D,
        0x8D,
        0x4D,
        0xCD,
        0x2D,
        0xAD,
        0x6D,
        0xED,
        0x1D,
        0x9D,
        0x5D,
        0xDD,
        0x3D,
        0xBD,
        0x7D,
        0xFD,
        0x03,
        0x83,
        0x43,
        0xC3,
        0x23,
        0xA3,
        0x63,
        0xE3,
        0x13,
        0x93,
        0x53,
        0xD3,
        0x33,
        0xB3,
        0x73,
        0xF3,
        0x0B,
        0x8B,
        0x4B,
        0xCB,
        0x2B,
        0xAB,
        0x6B,
        0xEB,
        0x1B,
        0x9B,
        0x5B,
        0xDB,
        0x3B,
        0xBB,
        0x7B,
        0xFB,
        0x07,
        0x87,
        0x47,
        0xC7,
        0x27,
        0xA7,
        0x67,
        0xE7,
        0x17,
        0x97,
        0x57,
        0xD7,
        0x37,
        0xB7,
        0x77,
        0xF7,
        0x0F,
        0x8F,
        0x4F,
        0xCF,
        0x2F,
        0xAF,
        0x6F,
        0xEF,
        0x1F,
        0x9F,
        0x5F,
        0xDF,
        0x3F,
        0xBF,
        0x7F,
        0xFF
    );

    /**
     * Pre-permuted S-box1
     *
     * Each box ($sbox1-$sbox8) has been vectorized, then each value pre-permuted using the
     * P table: concatenation can then be replaced by exclusive ORs.
     *
     * @var Array
     * @access private
     */
    var $sbox1 = array(
        0x00808200,
        0x00000000,
        0x00008000,
        0x00808202,
        0x00808002,
        0x00008202,
        0x00000002,
        0x00008000,
        0x00000200,
        0x00808200,
        0x00808202,
        0x00000200,
        0x00800202,
        0x00808002,
        0x00800000,
        0x00000002,
        0x00000202,
        0x00800200,
        0x00800200,
        0x00008200,
        0x00008200,
        0x00808000,
        0x00808000,
        0x00800202,
        0x00008002,
        0x00800002,
        0x00800002,
        0x00008002,
        0x00000000,
        0x00000202,
        0x00008202,
        0x00800000,
        0x00008000,
        0x00808202,
        0x00000002,
        0x00808000,
        0x00808200,
        0x00800000,
        0x00800000,
        0x00000200,
        0x00808002,
        0x00008000,
        0x00008200,
        0x00800002,
        0x00000200,
        0x00000002,
        0x00800202,
        0x00008202,
        0x00808202,
        0x00008002,
        0x00808000,
        0x00800202,
        0x00800002,
        0x00000202,
        0x00008202,
        0x00808200,
        0x00000202,
        0x00800200,
        0x00800200,
        0x00000000,
        0x00008002,
        0x00008200,
        0x00000000,
        0x00808002
    );

    /**
     * Pre-permuted S-box2
     *
     * @var Array
     * @access private
     */
    var $sbox2 = array(
        0x40084010,
        0x40004000,
        0x00004000,
        0x00084010,
        0x00080000,
        0x00000010,
        0x40080010,
        0x40004010,
        0x40000010,
        0x40084010,
        0x40084000,
        0x40000000,
        0x40004000,
        0x00080000,
        0x00000010,
        0x40080010,
        0x00084000,
        0x00080010,
        0x40004010,
        0x00000000,
        0x40000000,
        0x00004000,
        0x00084010,
        0x40080000,
        0x00080010,
        0x40000010,
        0x00000000,
        0x00084000,
        0x00004010,
        0x40084000,
        0x40080000,
        0x00004010,
        0x00000000,
        0x00084010,
        0x40080010,
        0x00080000,
        0x40004010,
        0x40080000,
        0x40084000,
        0x00004000,
        0x40080000,
        0x40004000,
        0x00000010,
        0x40084010,
        0x00084010,
        0x00000010,
        0x00004000,
        0x40000000,
        0x00004010,
        0x40084000,
        0x00080000,
        0x40000010,
        0x00080010,
        0x40004010,
        0x40000010,
        0x00080010,
        0x00084000,
        0x00000000,
        0x40004000,
        0x00004010,
        0x40000000,
        0x40080010,
        0x40084010,
        0x00084000
    );

    /**
     * Pre-permuted S-box3
     *
     * @var Array
     * @access private
     */
    var $sbox3 = array(
        0x00000104,
        0x04010100,
        0x00000000,
        0x04010004,
        0x04000100,
        0x00000000,
        0x00010104,
        0x04000100,
        0x00010004,
        0x04000004,
        0x04000004,
        0x00010000,
        0x04010104,
        0x00010004,
        0x04010000,
        0x00000104,
        0x04000000,
        0x00000004,
        0x04010100,
        0x00000100,
        0x00010100,
        0x04010000,
        0x04010004,
        0x00010104,
        0x04000104,
        0x00010100,
        0x00010000,
        0x04000104,
        0x00000004,
        0x04010104,
        0x00000100,
        0x04000000,
        0x04010100,
        0x04000000,
        0x00010004,
        0x00000104,
        0x00010000,
        0x04010100,
        0x04000100,
        0x00000000,
        0x00000100,
        0x00010004,
        0x04010104,
        0x04000100,
        0x04000004,
        0x00000100,
        0x00000000,
        0x04010004,
        0x04000104,
        0x00010000,
        0x04000000,
        0x04010104,
        0x00000004,
        0x00010104,
        0x00010100,
        0x04000004,
        0x04010000,
        0x04000104,
        0x00000104,
        0x04010000,
        0x00010104,
        0x00000004,
        0x04010004,
        0x00010100
    );

    /**
     * Pre-permuted S-box4
     *
     * @var Array
     * @access private
     */
    var $sbox4 = array(
        0x80401000,
        0x80001040,
        0x80001040,
        0x00000040,
        0x00401040,
        0x80400040,
        0x80400000,
        0x80001000,
        0x00000000,
        0x00401000,
        0x00401000,
        0x80401040,
        0x80000040,
        0x00000000,
        0x00400040,
        0x80400000,
        0x80000000,
        0x00001000,
        0x00400000,
        0x80401000,
        0x00000040,
        0x00400000,
        0x80001000,
        0x00001040,
        0x80400040,
        0x80000000,
        0x00001040,
        0x00400040,
        0x00001000,
        0x00401040,
        0x80401040,
        0x80000040,
        0x00400040,
        0x80400000,
        0x00401000,
        0x80401040,
        0x80000040,
        0x00000000,
        0x00000000,
        0x00401000,
        0x00001040,
        0x00400040,
        0x80400040,
        0x80000000,
        0x80401000,
        0x80001040,
        0x80001040,
        0x00000040,
        0x80401040,
        0x80000040,
        0x80000000,
        0x00001000,
        0x80400000,
        0x80001000,
        0x00401040,
        0x80400040,
        0x80001000,
        0x00001040,
        0x00400000,
        0x80401000,
        0x00000040,
        0x00400000,
        0x00001000,
        0x00401040
    );

    /**
     * Pre-permuted S-box5
     *
     * @var Array
     * @access private
     */
    var $sbox5 = array(
        0x00000080,
        0x01040080,
        0x01040000,
        0x21000080,
        0x00040000,
        0x00000080,
        0x20000000,
        0x01040000,
        0x20040080,
        0x00040000,
        0x01000080,
        0x20040080,
        0x21000080,
        0x21040000,
        0x00040080,
        0x20000000,
        0x01000000,
        0x20040000,
        0x20040000,
        0x00000000,
        0x20000080,
        0x21040080,
        0x21040080,
        0x01000080,
        0x21040000,
        0x20000080,
        0x00000000,
        0x21000000,
        0x01040080,
        0x01000000,
        0x21000000,
        0x00040080,
        0x00040000,
        0x21000080,
        0x00000080,
        0x01000000,
        0x20000000,
        0x01040000,
        0x21000080,
        0x20040080,
        0x01000080,
        0x20000000,
        0x21040000,
        0x01040080,
        0x20040080,
        0x00000080,
        0x01000000,
        0x21040000,
        0x21040080,
        0x00040080,
        0x21000000,
        0x21040080,
        0x01040000,
        0x00000000,
        0x20040000,
        0x21000000,
        0x00040080,
        0x01000080,
        0x20000080,
        0x00040000,
        0x00000000,
        0x20040000,
        0x01040080,
        0x20000080
    );

    /**
     * Pre-permuted S-box6
     *
     * @var Array
     * @access private
     */
    var $sbox6 = array(
        0x10000008,
        0x10200000,
        0x00002000,
        0x10202008,
        0x10200000,
        0x00000008,
        0x10202008,
        0x00200000,
        0x10002000,
        0x00202008,
        0x00200000,
        0x10000008,
        0x00200008,
        0x10002000,
        0x10000000,
        0x00002008,
        0x00000000,
        0x00200008,
        0x10002008,
        0x00002000,
        0x00202000,
        0x10002008,
        0x00000008,
        0x10200008,
        0x10200008,
        0x00000000,
        0x00202008,
        0x10202000,
        0x00002008,
        0x00202000,
        0x10202000,
        0x10000000,
        0x10002000,
        0x00000008,
        0x10200008,
        0x00202000,
        0x10202008,
        0x00200000,
        0x00002008,
        0x10000008,
        0x00200000,
        0x10002000,
        0x10000000,
        0x00002008,
        0x10000008,
        0x10202008,
        0x00202000,
        0x10200000,
        0x00202008,
        0x10202000,
        0x00000000,
        0x10200008,
        0x00000008,
        0x00002000,
        0x10200000,
        0x00202008,
        0x00002000,
        0x00200008,
        0x10002008,
        0x00000000,
        0x10202000,
        0x10000000,
        0x00200008,
        0x10002008
    );

    /**
     * Pre-permuted S-box7
     *
     * @var Array
     * @access private
     */
    var $sbox7 = array(
        0x00100000,
        0x02100001,
        0x02000401,
        0x00000000,
        0x00000400,
        0x02000401,
        0x00100401,
        0x02100400,
        0x02100401,
        0x00100000,
        0x00000000,
        0x02000001,
        0x00000001,
        0x02000000,
        0x02100001,
        0x00000401,
        0x02000400,
        0x00100401,
        0x00100001,
        0x02000400,
        0x02000001,
        0x02100000,
        0x02100400,
        0x00100001,
        0x02100000,
        0x00000400,
        0x00000401,
        0x02100401,
        0x00100400,
        0x00000001,
        0x02000000,
        0x00100400,
        0x02000000,
        0x00100400,
        0x00100000,
        0x02000401,
        0x02000401,
        0x02100001,
        0x02100001,
        0x00000001,
        0x00100001,
        0x02000000,
        0x02000400,
        0x00100000,
        0x02100400,
        0x00000401,
        0x00100401,
        0x02100400,
        0x00000401,
        0x02000001,
        0x02100401,
        0x02100000,
        0x00100400,
        0x00000000,
        0x00000001,
        0x02100401,
        0x00000000,
        0x00100401,
        0x02100000,
        0x00000400,
        0x02000001,
        0x02000400,
        0x00000400,
        0x00100001
    );

    /**
     * Pre-permuted S-box8
     *
     * @var Array
     * @access private
     */
    var $sbox8 = array(
        0x08000820,
        0x00000800,
        0x00020000,
        0x08020820,
        0x08000000,
        0x08000820,
        0x00000020,
        0x08000000,
        0x00020020,
        0x08020000,
        0x08020820,
        0x00020800,
        0x08020800,
        0x00020820,
        0x00000800,
        0x00000020,
        0x08020000,
        0x08000020,
        0x08000800,
        0x00000820,
        0x00020800,
        0x00020020,
        0x08020020,
        0x08020800,
        0x00000820,
        0x00000000,
        0x00000000,
        0x08020020,
        0x08000020,
        0x08000800,
        0x00020820,
        0x00020000,
        0x00020820,
        0x00020000,
        0x08020800,
        0x00000800,
        0x00000020,
        0x08020020,
        0x00000800,
        0x00020820,
        0x08000800,
        0x00000020,
        0x08000020,
        0x08020000,
        0x08020020,
        0x08000000,
        0x00020000,
        0x08000820,
        0x00000000,
        0x08020820,
        0x00020020,
        0x08000020,
        0x08020000,
        0x08000800,
        0x08000820,
        0x00000000,
        0x08020820,
        0x00020800,
        0x00020800,
        0x00000820,
        0x00000820,
        0x00020020,
        0x08000000,
        0x08020800
    );

    /**
     * Default Constructor.
     *
     * Determines whether or not the mcrypt extension should be used. $mode should only, at present, be
     * CRYPT_DES_MODE_ECB or CRYPT_DES_MODE_CBC. If not explictly set, CRYPT_DES_MODE_CBC will be used.
     *
     * @param
     *            optional Integer $mode
     * @return Crypt_DES
     * @access public
     */
    function __construct($mode = CRYPT_DES_MODE_CBC)
    {
        if (!defined('CRYPT_DES_MODE')) {
            switch (true) {
                case extension_loaded('mcrypt') && in_array('des', mcrypt_list_algorithms()):
                    define('CRYPT_DES_MODE', CRYPT_DES_MODE_MCRYPT);
                    break;
                default:
                    define('CRYPT_DES_MODE', CRYPT_DES_MODE_INTERNAL);
            }
        }
        
        switch (CRYPT_DES_MODE) {
            case CRYPT_DES_MODE_MCRYPT:
                switch ($mode) {
                    case CRYPT_DES_MODE_ECB:
                        $this->paddable = true;
                        $this->mode = MCRYPT_MODE_ECB;
                        break;
                    case CRYPT_DES_MODE_CTR:
                        $this->mode = 'ctr';
                        // $this->mode = in_array('ctr', mcrypt_list_modes()) ? 'ctr' : CRYPT_DES_MODE_CTR;
                        break;
                    case CRYPT_DES_MODE_CFB:
                        $this->mode = 'ncfb';
                        $this->ecb = mcrypt_module_open(MCRYPT_DES, '', MCRYPT_MODE_ECB, '');
                        break;
                    case CRYPT_DES_MODE_OFB:
                        $this->mode = MCRYPT_MODE_NOFB;
                        break;
                    case CRYPT_DES_MODE_CBC:
                    default:
                        $this->paddable = true;
                        $this->mode = MCRYPT_MODE_CBC;
                }
                $this->enmcrypt = mcrypt_module_open(MCRYPT_DES, '', $this->mode, '');
                $this->demcrypt = mcrypt_module_open(MCRYPT_DES, '', $this->mode, '');
                
                break;
            default:
                switch ($mode) {
                    case CRYPT_DES_MODE_ECB:
                    case CRYPT_DES_MODE_CBC:
                        $this->paddable = true;
                        $this->mode = $mode;
                        break;
                    case CRYPT_DES_MODE_CTR:
                    case CRYPT_DES_MODE_CFB:
                    case CRYPT_DES_MODE_OFB:
                        $this->mode = $mode;
                        break;
                    default:
                        $this->paddable = true;
                        $this->mode = CRYPT_DES_MODE_CBC;
                }
                if (function_exists('create_function') && is_callable('create_function')) {
                    $this->inline_crypt_setup();
                    $this->use_inline_crypt = true;
                }
        }
    }

    /**
     * Sets the key.
     *
     * Keys can be of any length. DES, itself, uses 64-bit keys (eg. strlen($key) == 8), however, we
     * only use the first eight, if $key has more then eight characters in it, and pad $key with the
     * null byte if it is less then eight characters long.
     *
     * DES also requires that every eighth bit be a parity bit, however, we'll ignore that.
     *
     * If the key is not explicitly set, it'll be assumed to be all zero's.
     *
     * @access public
     * @param String $key            
     */
    function setKey($key)
    {
        $this->keys = (CRYPT_DES_MODE == CRYPT_DES_MODE_MCRYPT) ? str_pad(substr($key, 0, 8), 8, chr(0)) : $this->_prepareKey($key);
        $this->enchanged = true;
        $this->dechanged = true;
    }

    /**
     * Sets the password.
     *
     * Depending on what $method is set to, setPassword()'s (optional) parameters are as follows:
     * {@link http://en.wikipedia.org/wiki/PBKDF2 pbkdf2}:
     * $hash, $salt, $count
     *
     * @param String $password            
     * @param
     *            optional String $method
     * @access public
     */
    function setPassword($password, $method = 'pbkdf2')
    {
        $key = '';
        
        switch ($method) {
            default: // 'pbkdf2'
                list (, , $hash, $salt, $count) = func_get_args();
                if (!isset($hash)) {
                    $hash = 'sha1';
                }
                // WPA and WPA2 use the SSID as the salt
                if (!isset($salt)) {
                    $salt = 'phpseclib/salt';
                }
                // RFC2898#section-4.2 uses 1,000 iterations by default
                // WPA and WPA2 use 4,096.
                if (!isset($count)) {
                    $count = 1000;
                }
                
                if (!class_exists('Crypt_Hash')) {
                    require_once ('Crypt/Hash.php');
                }
                
                $i = 1;
                while (strlen($key) < 8) { // $dkLen == 8
                                           // $dk.= $this->_pbkdf($password, $salt, $count, $i++);
                    $hmac = new Crypt_Hash();
                    $hmac->setHash($hash);
                    $hmac->setKey($password);
                    $f = $u = $hmac->hash($salt . pack('N', $i ++));
                    for ($j = 2; $j <= $count; $j ++) {
                        $u = $hmac->hash($u);
                        $f ^= $u;
                    }
                    $key .= $f;
                }
        }
        
        $this->setKey($key);
    }

    /**
     * Sets the initialization vector.
     * (optional)
     *
     * SetIV is not required when CRYPT_DES_MODE_ECB is being used. If not explictly set, it'll be assumed
     * to be all zero's.
     *
     * @access public
     * @param String $iv            
     */
    function setIV($iv)
    {
        $this->encryptIV = $this->decryptIV = $this->iv = str_pad(substr($iv, 0, 8), 8, chr(0));
        $this->enchanged = true;
        $this->dechanged = true;
    }

    /**
     * Generate CTR XOR encryption key
     *
     * Encrypt the output of this and XOR it against the ciphertext / plaintext to get the
     * plaintext / ciphertext in CTR mode.
     *
     * @see Crypt_DES::decrypt()
     * @see Crypt_DES::encrypt()
     * @access public
     * @param String $iv            
     */
    function _generate_xor(&$iv)
    {
        $xor = $iv;
        for ($j = 4; $j <= 8; $j += 4) {
            $temp = substr($iv, - $j, 4);
            switch ($temp) {
                case "\xFF\xFF\xFF\xFF":
                    $iv = substr_replace($iv, "\x00\x00\x00\x00", - $j, 4);
                    break;
                case "\x7F\xFF\xFF\xFF":
                    $iv = substr_replace($iv, "\x80\x00\x00\x00", - $j, 4);
                    break 2;
                default:
                    extract(unpack('Ncount', $temp));
                    $iv = substr_replace($iv, pack('N', $count + 1), - $j, 4);
                    break 2;
            }
        }
        
        return $xor;
    }

    /**
     * Encrypts a message.
     *
     * $plaintext will be padded with up to 8 additional bytes. Other DES implementations may or may not pad in the
     * same manner. Other common approaches to padding and the reasons why it's necessary are discussed in the following
     * URL:
     *
     * {@link http://www.di-mgt.com.au/cryptopad.html http://www.di-mgt.com.au/cryptopad.html}
     *
     * An alternative to padding is to, separately, send the length of the file. This is what SSH, in fact, does.
     * strlen($plaintext) will still need to be a multiple of 8, however, arbitrary values can be added to make it that
     * length.
     *
     * @see Crypt_DES::decrypt()
     * @access public
     * @param String $plaintext            
     */
    function encrypt($plaintext)
    {
        if ($this->paddable) {
            $plaintext = $this->_pad($plaintext);
        }
        
        if (CRYPT_DES_MODE == CRYPT_DES_MODE_MCRYPT) {
            if ($this->enchanged) {
                mcrypt_generic_init($this->enmcrypt, $this->keys, $this->encryptIV);
                if ($this->mode == 'ncfb') {
                    mcrypt_generic_init($this->ecb, $this->keys, "\0\0\0\0\0\0\0\0");
                }
                $this->enchanged = false;
            }
            
            if ($this->mode != 'ncfb' || ! $this->continuousBuffer) {
                $ciphertext = mcrypt_generic($this->enmcrypt, $plaintext);
            } else {
                $iv = &$this->encryptIV;
                $pos = &$this->enbuffer['pos'];
                $len = strlen($plaintext);
                $ciphertext = '';
                $i = 0;
                if ($pos) {
                    $orig_pos = $pos;
                    $max = 8 - $pos;
                    if ($len >= $max) {
                        $i = $max;
                        $len -= $max;
                        $pos = 0;
                    } else {
                        $i = $len;
                        $pos += $len;
                        $len = 0;
                    }
                    $ciphertext = substr($iv, $orig_pos) ^ $plaintext;
                    $iv = substr_replace($iv, $ciphertext, $orig_pos, $i);
                    $this->enbuffer['enmcrypt_init'] = true;
                }
                if ($len >= 8) {
                    if ($this->enbuffer['enmcrypt_init'] === false || $len > 600) {
                        if ($this->enbuffer['enmcrypt_init'] === true) {
                            mcrypt_generic_init($this->enmcrypt, $this->keys, $iv);
                            $this->enbuffer['enmcrypt_init'] = false;
                        }
                        $ciphertext .= mcrypt_generic($this->enmcrypt, substr($plaintext, $i, $len - $len % 8));
                        $iv = substr($ciphertext, - 8);
                        $len %= 8;
                    } else {
                        while ($len >= 8) {
                            $iv = mcrypt_generic($this->ecb, $iv) ^ substr($plaintext, $i, 8);
                            $ciphertext .= $iv;
                            $len -= 8;
                            $i += 8;
                        }
                    }
                }
                if ($len) {
                    $iv = mcrypt_generic($this->ecb, $iv);
                    $block = $iv ^ substr($plaintext, - $len);
                    $iv = substr_replace($iv, $block, 0, $len);
                    $ciphertext .= $block;
                    $pos = $len;
                }
                return $ciphertext;
            }
            
            if (!$this->continuousBuffer) {
                mcrypt_generic_init($this->enmcrypt, $this->keys, $this->encryptIV);
            }
            
            return $ciphertext;
        }
        
        if (!is_array($this->keys)) {
            $this->keys = $this->_prepareKey("\0\0\0\0\0\0\0\0");
        }
        
        if ($this->use_inline_crypt) {
            $inline = $this->inline_crypt;
            return $inline('encrypt', $this, $plaintext);
        }
        
        $buffer = &$this->enbuffer;
        $continuousBuffer = $this->continuousBuffer;
        $ciphertext = '';
        switch ($this->mode) {
            case CRYPT_DES_MODE_ECB:
                for ($i = 0; $i < strlen($plaintext); $i += 8) {
                    $ciphertext .= $this->_processBlock(substr($plaintext, $i, 8), CRYPT_DES_ENCRYPT);
                }
                break;
            case CRYPT_DES_MODE_CBC:
                $xor = $this->encryptIV;
                for ($i = 0; $i < strlen($plaintext); $i += 8) {
                    $block = substr($plaintext, $i, 8);
                    $block = $this->_processBlock($block ^ $xor, CRYPT_DES_ENCRYPT);
                    $xor = $block;
                    $ciphertext .= $block;
                }
                if ($this->continuousBuffer) {
                    $this->encryptIV = $xor;
                }
                break;
            case CRYPT_DES_MODE_CTR:
                $xor = $this->encryptIV;
                if (strlen($buffer['encrypted'])) {
                    for ($i = 0; $i < strlen($plaintext); $i += 8) {
                        $block = substr($plaintext, $i, 8);
                        if (strlen($block) > strlen($buffer['encrypted'])) {
                            $buffer['encrypted'] .= $this->_processBlock($this->_generate_xor($xor), CRYPT_DES_ENCRYPT);
                        }
                        $key = $this->_string_shift($buffer['encrypted']);
                        $ciphertext .= $block ^ $key;
                    }
                } else {
                    for ($i = 0; $i < strlen($plaintext); $i += 8) {
                        $block = substr($plaintext, $i, 8);
                        $key = $this->_processBlock($this->_generate_xor($xor), CRYPT_DES_ENCRYPT);
                        $ciphertext .= $block ^ $key;
                    }
                }
                if ($this->continuousBuffer) {
                    $this->encryptIV = $xor;
                    if ($start = strlen($plaintext) & 7) {
                        $buffer['encrypted'] = substr($key, $start) . $buffer['encrypted'];
                    }
                }
                break;
            case CRYPT_DES_MODE_CFB:
                if ($this->continuousBuffer) {
                    $iv = &$this->encryptIV;
                    $pos = &$buffer['pos'];
                } else {
                    $iv = $this->encryptIV;
                    $pos = 0;
                }
                $len = strlen($plaintext);
                $i = 0;
                if ($pos) {
                    $orig_pos = $pos;
                    $max = 8 - $pos;
                    if ($len >= $max) {
                        $i = $max;
                        $len -= $max;
                        $pos = 0;
                    } else {
                        $i = $len;
                        $pos += $len;
                        $len = 0;
                    }
                    $ciphertext = substr($iv, $orig_pos) ^ $plaintext;
                    $iv = substr_replace($iv, $ciphertext, $orig_pos, $i);
                }
                while ($len >= 8) {
                    $iv = $this->_processBlock($iv, CRYPT_DES_ENCRYPT) ^ substr($plaintext, $i, 8);
                    $ciphertext .= $iv;
                    $len -= 8;
                    $i += 8;
                }
                if ($len) {
                    $iv = $this->_processBlock($iv, CRYPT_DES_ENCRYPT);
                    $block = $iv ^ substr($plaintext, $i);
                    $iv = substr_replace($iv, $block, 0, $len);
                    $ciphertext .= $block;
                    $pos = $len;
                }
                return $ciphertext;
            case CRYPT_DES_MODE_OFB:
                $xor = $this->encryptIV;
                if (strlen($buffer['xor'])) {
                    for ($i = 0; $i < strlen($plaintext); $i += 8) {
                        $block = substr($plaintext, $i, 8);
                        if (strlen($block) > strlen($buffer['xor'])) {
                            $xor = $this->_processBlock($xor, CRYPT_DES_ENCRYPT);
                            $buffer['xor'] .= $xor;
                        }
                        $key = $this->_string_shift($buffer['xor']);
                        $ciphertext .= $block ^ $key;
                    }
                } else {
                    for ($i = 0; $i < strlen($plaintext); $i += 8) {
                        $xor = $this->_processBlock($xor, CRYPT_DES_ENCRYPT);
                        $ciphertext .= substr($plaintext, $i, 8) ^ $xor;
                    }
                    $key = $xor;
                }
                if ($this->continuousBuffer) {
                    $this->encryptIV = $xor;
                    if ($start = strlen($plaintext) & 7) {
                        $buffer['xor'] = substr($key, $start) . $buffer['xor'];
                    }
                }
        }
        
        return $ciphertext;
    }

    /**
     * Decrypts a message.
     *
     * If strlen($ciphertext) is not a multiple of 8, null bytes will be added to the end of the string until it is.
     *
     * @see Crypt_DES::encrypt()
     * @access public
     * @param String $ciphertext            
     */
    function decrypt($ciphertext)
    {
        if ($this->paddable) {
            // we pad with chr(0) since that's what mcrypt_generic does. to quote from http://php.net/function.mcrypt-generic :
            // "The data is padded with "\0" to make sure the length of the data is n * blocksize."
            $ciphertext = str_pad($ciphertext, (strlen($ciphertext) + 7) & 0xFFFFFFF8, chr(0));
        }
        
        if (CRYPT_DES_MODE == CRYPT_DES_MODE_MCRYPT) {
            if ($this->dechanged) {
                mcrypt_generic_init($this->demcrypt, $this->keys, $this->decryptIV);
                if ($this->mode == 'ncfb') {
                    mcrypt_generic_init($this->ecb, $this->keys, "\0\0\0\0\0\0\0\0");
                }
                $this->dechanged = false;
            }
            
            if ($this->mode != 'ncfb' || ! $this->continuousBuffer) {
                $plaintext = mdecrypt_generic($this->demcrypt, $ciphertext);
            } else {
                $iv = &$this->decryptIV;
                $pos = &$this->debuffer['pos'];
                $len = strlen($ciphertext);
                $plaintext = '';
                $i = 0;
                if ($pos) {
                    $orig_pos = $pos;
                    $max = 8 - $pos;
                    if ($len >= $max) {
                        $i = $max;
                        $len -= $max;
                        $pos = 0;
                    } else {
                        $i = $len;
                        $pos += $len;
                        $len = 0;
                    }
                    $plaintext = substr($iv, $orig_pos) ^ $ciphertext;
                    $iv = substr_replace($iv, substr($ciphertext, 0, $i), $orig_pos, $i);
                }
                if ($len >= 8) {
                    $cb = substr($ciphertext, $i, $len - $len % 8);
                    $plaintext .= mcrypt_generic($this->ecb, $iv . $cb) ^ $cb;
                    $iv = substr($cb, - 8);
                    $len %= 8;
                }
                if ($len) {
                    $iv = mcrypt_generic($this->ecb, $iv);
                    $plaintext .= $iv ^ substr($ciphertext, - $len);
                    $iv = substr_replace($iv, substr($ciphertext, - $len), 0, $len);
                    $pos = $len;
                }
                return $plaintext;
            }
            
            if (!$this->continuousBuffer) {
                mcrypt_generic_init($this->demcrypt, $this->keys, $this->decryptIV);
            }
            
            return $this->paddable ? $this->_unpad($plaintext) : $plaintext;
        }
        
        if (!is_array($this->keys)) {
            $this->keys = $this->_prepareKey("\0\0\0\0\0\0\0\0");
        }
        
        if ($this->use_inline_crypt) {
            $inline = $this->inline_crypt;
            return $inline('decrypt', $this, $ciphertext);
        }
        
        $buffer = &$this->debuffer;
        $continuousBuffer = $this->continuousBuffer;
        $plaintext = '';
        switch ($this->mode) {
            case CRYPT_DES_MODE_ECB:
                for ($i = 0; $i < strlen($ciphertext); $i += 8) {
                    $plaintext .= $this->_processBlock(substr($ciphertext, $i, 8), CRYPT_DES_DECRYPT);
                }
                break;
            case CRYPT_DES_MODE_CBC:
                $xor = $this->decryptIV;
                for ($i = 0; $i < strlen($ciphertext); $i += 8) {
                    $block = substr($ciphertext, $i, 8);
                    $plaintext .= $this->_processBlock($block, CRYPT_DES_DECRYPT) ^ $xor;
                    $xor = $block;
                }
                if ($this->continuousBuffer) {
                    $this->decryptIV = $xor;
                }
                break;
            case CRYPT_DES_MODE_CTR:
                $xor = $this->decryptIV;
                if (strlen($buffer['ciphertext'])) {
                    for ($i = 0; $i < strlen($ciphertext); $i += 8) {
                        $block = substr($ciphertext, $i, 8);
                        if (strlen($block) > strlen($buffer['ciphertext'])) {
                            $buffer['ciphertext'] .= $this->_processBlock($this->_generate_xor($xor), CRYPT_DES_ENCRYPT);
                        }
                        $key = $this->_string_shift($buffer['ciphertext']);
                        $plaintext .= $block ^ $key;
                    }
                } else {
                    for ($i = 0; $i < strlen($ciphertext); $i += 8) {
                        $block = substr($ciphertext, $i, 8);
                        $key = $this->_processBlock($this->_generate_xor($xor), CRYPT_DES_ENCRYPT);
                        $plaintext .= $block ^ $key;
                    }
                }
                if ($this->continuousBuffer) {
                    $this->decryptIV = $xor;
                    if ($start = strlen($ciphertext) % 8) {
                        $buffer['ciphertext'] = substr($key, $start) . $buffer['ciphertext'];
                    }
                }
                break;
            case CRYPT_DES_MODE_CFB:
                if ($this->continuousBuffer) {
                    $iv = &$this->decryptIV;
                    $pos = &$buffer['pos'];
                } else {
                    $iv = $this->decryptIV;
                    $pos = 0;
                }
                $len = strlen($ciphertext);
                $i = 0;
                if ($pos) {
                    $orig_pos = $pos;
                    $max = 8 - $pos;
                    if ($len >= $max) {
                        $i = $max;
                        $len -= $max;
                        $pos = 0;
                    } else {
                        $i = $len;
                        $pos += $len;
                        $len = 0;
                    }
                    $plaintext = substr($iv, $orig_pos) ^ $ciphertext;
                    $iv = substr_replace($iv, substr($ciphertext, 0, $i), $orig_pos, $i);
                }
                while ($len >= 8) {
                    $iv = $this->_processBlock($iv, CRYPT_DES_ENCRYPT);
                    $cb = substr($ciphertext, $i, 8);
                    $plaintext .= $iv ^ $cb;
                    $iv = $cb;
                    $len -= 8;
                    $i += 8;
                }
                if ($len) {
                    $iv = $this->_processBlock($iv, CRYPT_DES_ENCRYPT);
                    $plaintext .= $iv ^ substr($ciphertext, $i);
                    $iv = substr_replace($iv, substr($ciphertext, $i), 0, $len);
                    $pos = $len;
                }
                return $plaintext;
            case CRYPT_DES_MODE_OFB:
                $xor = $this->decryptIV;
                if (strlen($buffer['xor'])) {
                    for ($i = 0; $i < strlen($ciphertext); $i += 8) {
                        $block = substr($ciphertext, $i, 8);
                        if (strlen($block) > strlen($buffer['xor'])) {
                            $xor = $this->_processBlock($xor, CRYPT_DES_ENCRYPT);
                            $buffer['xor'] .= $xor;
                        }
                        $key = $this->_string_shift($buffer['xor']);
                        $plaintext .= $block ^ $key;
                    }
                } else {
                    for ($i = 0; $i < strlen($ciphertext); $i += 8) {
                        $xor = $this->_processBlock($xor, CRYPT_DES_ENCRYPT);
                        $plaintext .= substr($ciphertext, $i, 8) ^ $xor;
                    }
                    $key = $xor;
                }
                if ($this->continuousBuffer) {
                    $this->decryptIV = $xor;
                    if ($start = strlen($ciphertext) % 8) {
                        $buffer['xor'] = substr($key, $start) . $buffer['xor'];
                    }
                }
        }
        
        return $this->paddable ? $this->_unpad($plaintext) : $plaintext;
    }

    /**
     * Treat consecutive "packets" as if they are a continuous buffer.
     *
     * Say you have a 16-byte plaintext $plaintext. Using the default behavior, the two following code snippets
     * will yield different outputs:
     *
     * <code>
     * echo $des->encrypt(substr($plaintext, 0, 8));
     * echo $des->encrypt(substr($plaintext, 8, 8));
     * </code>
     * <code>
     * echo $des->encrypt($plaintext);
     * </code>
     *
     * The solution is to enable the continuous buffer. Although this will resolve the above discrepancy, it creates
     * another, as demonstrated with the following:
     *
     * <code>
     * $des->encrypt(substr($plaintext, 0, 8));
     * echo $des->decrypt($des->encrypt(substr($plaintext, 8, 8)));
     * </code>
     * <code>
     * echo $des->decrypt($des->encrypt(substr($plaintext, 8, 8)));
     * </code>
     *
     * With the continuous buffer disabled, these would yield the same output. With it enabled, they yield different
     * outputs. The reason is due to the fact that the initialization vector's change after every encryption /
     * decryption round when the continuous buffer is enabled. When it's disabled, they remain constant.
     *
     * Put another way, when the continuous buffer is enabled, the state of the Crypt_DES() object changes after each
     * encryption / decryption round, whereas otherwise, it'd remain constant. For this reason, it's recommended that
     * continuous buffers not be used. They do offer better security and are, in fact, sometimes required (SSH uses them),
     * however, they are also less intuitive and more likely to cause you problems.
     *
     * @see Crypt_DES::disableContinuousBuffer()
     * @access public
     */
    function enableContinuousBuffer()
    {
        $this->continuousBuffer = true;
    }

    /**
     * Treat consecutive packets as if they are a discontinuous buffer.
     *
     * The default behavior.
     *
     * @see Crypt_DES::enableContinuousBuffer()
     * @access public
     */
    function disableContinuousBuffer()
    {
        $this->continuousBuffer = false;
        $this->encryptIV = $this->iv;
        $this->decryptIV = $this->iv;
        $this->enbuffer = array(
            'encrypted' => '',
            'xor' => '',
            'pos' => 0,
            'enmcrypt_init' => true
        );
        $this->debuffer = array(
            'ciphertext' => '',
            'xor' => '',
            'pos' => 0,
            'demcrypt_init' => true
        );
        
        if (CRYPT_DES_MODE == CRYPT_DES_MODE_MCRYPT) {
            mcrypt_generic_init($this->enmcrypt, $this->keys, $this->iv);
            mcrypt_generic_init($this->demcrypt, $this->keys, $this->iv);
        }
    }

    /**
     * Pad "packets".
     *
     * DES works by encrypting eight bytes at a time. If you ever need to encrypt or decrypt something that's not
     * a multiple of eight, it becomes necessary to pad the input so that it's length is a multiple of eight.
     *
     * Padding is enabled by default. Sometimes, however, it is undesirable to pad strings. Such is the case in SSH1,
     * where "packets" are padded with random bytes before being encrypted. Unpad these packets and you risk stripping
     * away characters that shouldn't be stripped away. (SSH knows how many bytes are added because the length is
     * transmitted separately)
     *
     * @see Crypt_DES::disablePadding()
     * @access public
     */
    function enablePadding()
    {
        $this->padding = true;
    }

    /**
     * Do not pad packets.
     *
     * @see Crypt_DES::enablePadding()
     * @access public
     */
    function disablePadding()
    {
        $this->padding = false;
    }

    /**
     * Pads a string
     *
     * Pads a string using the RSA PKCS padding standards so that its length is a multiple of the blocksize (8).
     * 8 - (strlen($text) & 7) bytes are added, each of which is equal to chr(8 - (strlen($text) & 7)
     *
     * If padding is disabled and $text is not a multiple of the blocksize, the string will be padded regardless
     * and padding will, hence forth, be enabled.
     *
     * @see Crypt_DES::_unpad()
     * @access private
     */
    function _pad($text)
    {
        $length = strlen($text);
        
        if (!$this->padding) {
            if (($length & 7) == 0) {
                return $text;
            } else {
                user_error("The plaintext's length ($length) is not a multiple of the block size (8)");
                $this->padding = true;
            }
        }
        
        $pad = 8 - ($length & 7);
        return str_pad($text, $length + $pad, chr($pad));
    }

    /**
     * Unpads a string
     *
     * If padding is enabled and the reported padding length is invalid the encryption key will be assumed to be wrong
     * and false will be returned.
     *
     * @see Crypt_DES::_pad()
     * @access private
     */
    function _unpad($text)
    {
        if (!$this->padding) {
            return $text;
        }
        
        $length = ord($text[strlen($text) - 1]);
        
        if (!$length || $length > 8) {
            return false;
        }
        
        return substr($text, 0, - $length);
    }

    /**
     * Encrypts or decrypts a 64-bit block
     *
     * $mode should be either CRYPT_DES_ENCRYPT or CRYPT_DES_DECRYPT. See
     * {@link http://en.wikipedia.org/wiki/Image:Feistel.png Feistel.png} to get a general
     * idea of what this function does.
     *
     * @access private
     * @param String $block            
     * @param Integer $mode            
     * @return String
     */
    function _processBlock($block, $mode)
    {
        $shuffle = $this->shuffle;
        $invipmap = $this->invipmap;
        $ipmap = $this->ipmap;
        $sbox1 = $this->sbox1;
        $sbox2 = $this->sbox2;
        $sbox3 = $this->sbox3;
        $sbox4 = $this->sbox4;
        $sbox5 = $this->sbox5;
        $sbox6 = $this->sbox6;
        $sbox7 = $this->sbox7;
        $sbox8 = $this->sbox8;
        $keys = $this->keys[$mode];
        
        // Do the initial IP permutation.
        $t = unpack('Nl/Nr', $block);
        list ($l, $r) = array(
            $t['l'],
            $t['r']
        );
        $block = ($shuffle[$ipmap[$r & 0xFF]] & "\x80\x80\x80\x80\x80\x80\x80\x80") | ($shuffle[$ipmap[($r >> 8) & 0xFF]] & "\x40\x40\x40\x40\x40\x40\x40\x40") | ($shuffle[$ipmap[($r >> 16) & 0xFF]] & "\x20\x20\x20\x20\x20\x20\x20\x20") | ($shuffle[$ipmap[($r >> 24) & 0xFF]] & "\x10\x10\x10\x10\x10\x10\x10\x10") | ($shuffle[$ipmap[$l & 0xFF]] & "\x08\x08\x08\x08\x08\x08\x08\x08") | ($shuffle[$ipmap[($l >> 8) & 0xFF]] & "\x04\x04\x04\x04\x04\x04\x04\x04") | ($shuffle[$ipmap[($l >> 16) & 0xFF]] & "\x02\x02\x02\x02\x02\x02\x02\x02") | ($shuffle[$ipmap[($l >> 24) & 0xFF]] & "\x01\x01\x01\x01\x01\x01\x01\x01");
        
        // Extract L0 and R0.
        $t = unpack('Nl/Nr', $block);
        list ($l, $r) = array(
            $t['l'],
            $t['r']
        );
        
        // Perform the 16 steps.
        for ($i = 0; $i < 16; $i ++) {
            // start of "the Feistel (F) function" - see the following URL:
            // http://en.wikipedia.org/wiki/Image:Data_Encryption_Standard_InfoBox_Diagram.png
            // Merge key schedule.
            $b1 = (($r >> 3) & 0x1FFFFFFF) ^ ($r << 29) ^ $keys[$i][0];
            $b2 = (($r >> 31) & 0x00000001) ^ ($r << 1) ^ $keys[$i][1];
            
            // S-box indexing.
            $t = $sbox1[($b1 >> 24) & 0x3F] ^ $sbox2[($b2 >> 24) & 0x3F] ^ $sbox3[($b1 >> 16) & 0x3F] ^ $sbox4[($b2 >> 16) & 0x3F] ^ $sbox5[($b1 >> 8) & 0x3F] ^ $sbox6[($b2 >> 8) & 0x3F] ^ $sbox7[$b1 & 0x3F] ^ $sbox8[$b2 & 0x3F] ^ $l;
            // end of "the Feistel (F) function"
            
            $l = $r;
            $r = $t;
        }
        
        // Perform the inverse IP permutation.
        return ($shuffle[$invipmap[($l >> 24) & 0xFF]] & "\x80\x80\x80\x80\x80\x80\x80\x80") | ($shuffle[$invipmap[($r >> 24) & 0xFF]] & "\x40\x40\x40\x40\x40\x40\x40\x40") | ($shuffle[$invipmap[($l >> 16) & 0xFF]] & "\x20\x20\x20\x20\x20\x20\x20\x20") | ($shuffle[$invipmap[($r >> 16) & 0xFF]] & "\x10\x10\x10\x10\x10\x10\x10\x10") | ($shuffle[$invipmap[($l >> 8) & 0xFF]] & "\x08\x08\x08\x08\x08\x08\x08\x08") | ($shuffle[$invipmap[($r >> 8) & 0xFF]] & "\x04\x04\x04\x04\x04\x04\x04\x04") | ($shuffle[$invipmap[$l & 0xFF]] & "\x02\x02\x02\x02\x02\x02\x02\x02") | ($shuffle[$invipmap[$r & 0xFF]] & "\x01\x01\x01\x01\x01\x01\x01\x01");
    }

    /**
     * Creates the key schedule.
     *
     * @access private
     * @param String $key            
     * @return Array
     */
    function _prepareKey($key)
    {
        static $shifts = array( // number of key bits shifted per round
            1,
            1,
            2,
            2,
            2,
            2,
            2,
            2,
            1,
            2,
            2,
            2,
            2,
            2,
            2,
            1
        );
        
        static $pc1map = array(
            0x00,
            0x00,
            0x08,
            0x08,
            0x04,
            0x04,
            0x0C,
            0x0C,
            0x02,
            0x02,
            0x0A,
            0x0A,
            0x06,
            0x06,
            0x0E,
            0x0E,
            0x10,
            0x10,
            0x18,
            0x18,
            0x14,
            0x14,
            0x1C,
            0x1C,
            0x12,
            0x12,
            0x1A,
            0x1A,
            0x16,
            0x16,
            0x1E,
            0x1E,
            0x20,
            0x20,
            0x28,
            0x28,
            0x24,
            0x24,
            0x2C,
            0x2C,
            0x22,
            0x22,
            0x2A,
            0x2A,
            0x26,
            0x26,
            0x2E,
            0x2E,
            0x30,
            0x30,
            0x38,
            0x38,
            0x34,
            0x34,
            0x3C,
            0x3C,
            0x32,
            0x32,
            0x3A,
            0x3A,
            0x36,
            0x36,
            0x3E,
            0x3E,
            0x40,
            0x40,
            0x48,
            0x48,
            0x44,
            0x44,
            0x4C,
            0x4C,
            0x42,
            0x42,
            0x4A,
            0x4A,
            0x46,
            0x46,
            0x4E,
            0x4E,
            0x50,
            0x50,
            0x58,
            0x58,
            0x54,
            0x54,
            0x5C,
            0x5C,
            0x52,
            0x52,
            0x5A,
            0x5A,
            0x56,
            0x56,
            0x5E,
            0x5E,
            0x60,
            0x60,
            0x68,
            0x68,
            0x64,
            0x64,
            0x6C,
            0x6C,
            0x62,
            0x62,
            0x6A,
            0x6A,
            0x66,
            0x66,
            0x6E,
            0x6E,
            0x70,
            0x70,
            0x78,
            0x78,
            0x74,
            0x74,
            0x7C,
            0x7C,
            0x72,
            0x72,
            0x7A,
            0x7A,
            0x76,
            0x76,
            0x7E,
            0x7E,
            0x80,
            0x80,
            0x88,
            0x88,
            0x84,
            0x84,
            0x8C,
            0x8C,
            0x82,
            0x82,
            0x8A,
            0x8A,
            0x86,
            0x86,
            0x8E,
            0x8E,
            0x90,
            0x90,
            0x98,
            0x98,
            0x94,
            0x94,
            0x9C,
            0x9C,
            0x92,
            0x92,
            0x9A,
            0x9A,
            0x96,
            0x96,
            0x9E,
            0x9E,
            0xA0,
            0xA0,
            0xA8,
            0xA8,
            0xA4,
            0xA4,
            0xAC,
            0xAC,
            0xA2,
            0xA2,
            0xAA,
            0xAA,
            0xA6,
            0xA6,
            0xAE,
            0xAE,
            0xB0,
            0xB0,
            0xB8,
            0xB8,
            0xB4,
            0xB4,
            0xBC,
            0xBC,
            0xB2,
            0xB2,
            0xBA,
            0xBA,
            0xB6,
            0xB6,
            0xBE,
            0xBE,
            0xC0,
            0xC0,
            0xC8,
            0xC8,
            0xC4,
            0xC4,
            0xCC,
            0xCC,
            0xC2,
            0xC2,
            0xCA,
            0xCA,
            0xC6,
            0xC6,
            0xCE,
            0xCE,
            0xD0,
            0xD0,
            0xD8,
            0xD8,
            0xD4,
            0xD4,
            0xDC,
            0xDC,
            0xD2,
            0xD2,
            0xDA,
            0xDA,
            0xD6,
            0xD6,
            0xDE,
            0xDE,
            0xE0,
            0xE0,
            0xE8,
            0xE8,
            0xE4,
            0xE4,
            0xEC,
            0xEC,
            0xE2,
            0xE2,
            0xEA,
            0xEA,
            0xE6,
            0xE6,
            0xEE,
            0xEE,
            0xF0,
            0xF0,
            0xF8,
            0xF8,
            0xF4,
            0xF4,
            0xFC,
            0xFC,
            0xF2,
            0xF2,
            0xFA,
            0xFA,
            0xF6,
            0xF6,
            0xFE,
            0xFE
        );
        
        // Mapping tables for the PC-2 transformation.
        static $pc2mapc1 = array(
            0x00000000,
            0x00000400,
            0x00200000,
            0x00200400,
            0x00000001,
            0x00000401,
            0x00200001,
            0x00200401,
            0x02000000,
            0x02000400,
            0x02200000,
            0x02200400,
            0x02000001,
            0x02000401,
            0x02200001,
            0x02200401
        );
        static $pc2mapc2 = array(
            0x00000000,
            0x00000800,
            0x08000000,
            0x08000800,
            0x00010000,
            0x00010800,
            0x08010000,
            0x08010800,
            0x00000000,
            0x00000800,
            0x08000000,
            0x08000800,
            0x00010000,
            0x00010800,
            0x08010000,
            0x08010800,
            0x00000100,
            0x00000900,
            0x08000100,
            0x08000900,
            0x00010100,
            0x00010900,
            0x08010100,
            0x08010900,
            0x00000100,
            0x00000900,
            0x08000100,
            0x08000900,
            0x00010100,
            0x00010900,
            0x08010100,
            0x08010900,
            0x00000010,
            0x00000810,
            0x08000010,
            0x08000810,
            0x00010010,
            0x00010810,
            0x08010010,
            0x08010810,
            0x00000010,
            0x00000810,
            0x08000010,
            0x08000810,
            0x00010010,
            0x00010810,
            0x08010010,
            0x08010810,
            0x00000110,
            0x00000910,
            0x08000110,
            0x08000910,
            0x00010110,
            0x00010910,
            0x08010110,
            0x08010910,
            0x00000110,
            0x00000910,
            0x08000110,
            0x08000910,
            0x00010110,
            0x00010910,
            0x08010110,
            0x08010910,
            0x00040000,
            0x00040800,
            0x08040000,
            0x08040800,
            0x00050000,
            0x00050800,
            0x08050000,
            0x08050800,
            0x00040000,
            0x00040800,
            0x08040000,
            0x08040800,
            0x00050000,
            0x00050800,
            0x08050000,
            0x08050800,
            0x00040100,
            0x00040900,
            0x08040100,
            0x08040900,
            0x00050100,
            0x00050900,
            0x08050100,
            0x08050900,
            0x00040100,
            0x00040900,
            0x08040100,
            0x08040900,
            0x00050100,
            0x00050900,
            0x08050100,
            0x08050900,
            0x00040010,
            0x00040810,
            0x08040010,
            0x08040810,
            0x00050010,
            0x00050810,
            0x08050010,
            0x08050810,
            0x00040010,
            0x00040810,
            0x08040010,
            0x08040810,
            0x00050010,
            0x00050810,
            0x08050010,
            0x08050810,
            0x00040110,
            0x00040910,
            0x08040110,
            0x08040910,
            0x00050110,
            0x00050910,
            0x08050110,
            0x08050910,
            0x00040110,
            0x00040910,
            0x08040110,
            0x08040910,
            0x00050110,
            0x00050910,
            0x08050110,
            0x08050910,
            0x01000000,
            0x01000800,
            0x09000000,
            0x09000800,
            0x01010000,
            0x01010800,
            0x09010000,
            0x09010800,
            0x01000000,
            0x01000800,
            0x09000000,
            0x09000800,
            0x01010000,
            0x01010800,
            0x09010000,
            0x09010800,
            0x01000100,
            0x01000900,
            0x09000100,
            0x09000900,
            0x01010100,
            0x01010900,
            0x09010100,
            0x09010900,
            0x01000100,
            0x01000900,
            0x09000100,
            0x09000900,
            0x01010100,
            0x01010900,
            0x09010100,
            0x09010900,
            0x01000010,
            0x01000810,
            0x09000010,
            0x09000810,
            0x01010010,
            0x01010810,
            0x09010010,
            0x09010810,
            0x01000010,
            0x01000810,
            0x09000010,
            0x09000810,
            0x01010010,
            0x01010810,
            0x09010010,
            0x09010810,
            0x01000110,
            0x01000910,
            0x09000110,
            0x09000910,
            0x01010110,
            0x01010910,
            0x09010110,
            0x09010910,
            0x01000110,
            0x01000910,
            0x09000110,
            0x09000910,
            0x01010110,
            0x01010910,
            0x09010110,
            0x09010910,
            0x01040000,
            0x01040800,
            0x09040000,
            0x09040800,
            0x01050000,
            0x01050800,
            0x09050000,
            0x09050800,
            0x01040000,
            0x01040800,
            0x09040000,
            0x09040800,
            0x01050000,
            0x01050800,
            0x09050000,
            0x09050800,
            0x01040100,
            0x01040900,
            0x09040100,
            0x09040900,
            0x01050100,
            0x01050900,
            0x09050100,
            0x09050900,
            0x01040100,
            0x01040900,
            0x09040100,
            0x09040900,
            0x01050100,
            0x01050900,
            0x09050100,
            0x09050900,
            0x01040010,
            0x01040810,
            0x09040010,
            0x09040810,
            0x01050010,
            0x01050810,
            0x09050010,
            0x09050810,
            0x01040010,
            0x01040810,
            0x09040010,
            0x09040810,
            0x01050010,
            0x01050810,
            0x09050010,
            0x09050810,
            0x01040110,
            0x01040910,
            0x09040110,
            0x09040910,
            0x01050110,
            0x01050910,
            0x09050110,
            0x09050910,
            0x01040110,
            0x01040910,
            0x09040110,
            0x09040910,
            0x01050110,
            0x01050910,
            0x09050110,
            0x09050910
        );
        static $pc2mapc3 = array(
            0x00000000,
            0x00000004,
            0x00001000,
            0x00001004,
            0x00000000,
            0x00000004,
            0x00001000,
            0x00001004,
            0x10000000,
            0x10000004,
            0x10001000,
            0x10001004,
            0x10000000,
            0x10000004,
            0x10001000,
            0x10001004,
            0x00000020,
            0x00000024,
            0x00001020,
            0x00001024,
            0x00000020,
            0x00000024,
            0x00001020,
            0x00001024,
            0x10000020,
            0x10000024,
            0x10001020,
            0x10001024,
            0x10000020,
            0x10000024,
            0x10001020,
            0x10001024,
            0x00080000,
            0x00080004,
            0x00081000,
            0x00081004,
            0x00080000,
            0x00080004,
            0x00081000,
            0x00081004,
            0x10080000,
            0x10080004,
            0x10081000,
            0x10081004,
            0x10080000,
            0x10080004,
            0x10081000,
            0x10081004,
            0x00080020,
            0x00080024,
            0x00081020,
            0x00081024,
            0x00080020,
            0x00080024,
            0x00081020,
            0x00081024,
            0x10080020,
            0x10080024,
            0x10081020,
            0x10081024,
            0x10080020,
            0x10080024,
            0x10081020,
            0x10081024,
            0x20000000,
            0x20000004,
            0x20001000,
            0x20001004,
            0x20000000,
            0x20000004,
            0x20001000,
            0x20001004,
            0x30000000,
            0x30000004,
            0x30001000,
            0x30001004,
            0x30000000,
            0x30000004,
            0x30001000,
            0x30001004,
            0x20000020,
            0x20000024,
            0x20001020,
            0x20001024,
            0x20000020,
            0x20000024,
            0x20001020,
            0x20001024,
            0x30000020,
            0x30000024,
            0x30001020,
            0x30001024,
            0x30000020,
            0x30000024,
            0x30001020,
            0x30001024,
            0x20080000,
            0x20080004,
            0x20081000,
            0x20081004,
            0x20080000,
            0x20080004,
            0x20081000,
            0x20081004,
            0x30080000,
            0x30080004,
            0x30081000,
            0x30081004,
            0x30080000,
            0x30080004,
            0x30081000,
            0x30081004,
            0x20080020,
            0x20080024,
            0x20081020,
            0x20081024,
            0x20080020,
            0x20080024,
            0x20081020,
            0x20081024,
            0x30080020,
            0x30080024,
            0x30081020,
            0x30081024,
            0x30080020,
            0x30080024,
            0x30081020,
            0x30081024,
            0x00000002,
            0x00000006,
            0x00001002,
            0x00001006,
            0x00000002,
            0x00000006,
            0x00001002,
            0x00001006,
            0x10000002,
            0x10000006,
            0x10001002,
            0x10001006,
            0x10000002,
            0x10000006,
            0x10001002,
            0x10001006,
            0x00000022,
            0x00000026,
            0x00001022,
            0x00001026,
            0x00000022,
            0x00000026,
            0x00001022,
            0x00001026,
            0x10000022,
            0x10000026,
            0x10001022,
            0x10001026,
            0x10000022,
            0x10000026,
            0x10001022,
            0x10001026,
            0x00080002,
            0x00080006,
            0x00081002,
            0x00081006,
            0x00080002,
            0x00080006,
            0x00081002,
            0x00081006,
            0x10080002,
            0x10080006,
            0x10081002,
            0x10081006,
            0x10080002,
            0x10080006,
            0x10081002,
            0x10081006,
            0x00080022,
            0x00080026,
            0x00081022,
            0x00081026,
            0x00080022,
            0x00080026,
            0x00081022,
            0x00081026,
            0x10080022,
            0x10080026,
            0x10081022,
            0x10081026,
            0x10080022,
            0x10080026,
            0x10081022,
            0x10081026,
            0x20000002,
            0x20000006,
            0x20001002,
            0x20001006,
            0x20000002,
            0x20000006,
            0x20001002,
            0x20001006,
            0x30000002,
            0x30000006,
            0x30001002,
            0x30001006,
            0x30000002,
            0x30000006,
            0x30001002,
            0x30001006,
            0x20000022,
            0x20000026,
            0x20001022,
            0x20001026,
            0x20000022,
            0x20000026,
            0x20001022,
            0x20001026,
            0x30000022,
            0x30000026,
            0x30001022,
            0x30001026,
            0x30000022,
            0x30000026,
            0x30001022,
            0x30001026,
            0x20080002,
            0x20080006,
            0x20081002,
            0x20081006,
            0x20080002,
            0x20080006,
            0x20081002,
            0x20081006,
            0x30080002,
            0x30080006,
            0x30081002,
            0x30081006,
            0x30080002,
            0x30080006,
            0x30081002,
            0x30081006,
            0x20080022,
            0x20080026,
            0x20081022,
            0x20081026,
            0x20080022,
            0x20080026,
            0x20081022,
            0x20081026,
            0x30080022,
            0x30080026,
            0x30081022,
            0x30081026,
            0x30080022,
            0x30080026,
            0x30081022,
            0x30081026
        );
        static $pc2mapc4 = array(
            0x00000000,
            0x00100000,
            0x00000008,
            0x00100008,
            0x00000200,
            0x00100200,
            0x00000208,
            0x00100208,
            0x00000000,
            0x00100000,
            0x00000008,
            0x00100008,
            0x00000200,
            0x00100200,
            0x00000208,
            0x00100208,
            0x04000000,
            0x04100000,
            0x04000008,
            0x04100008,
            0x04000200,
            0x04100200,
            0x04000208,
            0x04100208,
            0x04000000,
            0x04100000,
            0x04000008,
            0x04100008,
            0x04000200,
            0x04100200,
            0x04000208,
            0x04100208,
            0x00002000,
            0x00102000,
            0x00002008,
            0x00102008,
            0x00002200,
            0x00102200,
            0x00002208,
            0x00102208,
            0x00002000,
            0x00102000,
            0x00002008,
            0x00102008,
            0x00002200,
            0x00102200,
            0x00002208,
            0x00102208,
            0x04002000,
            0x04102000,
            0x04002008,
            0x04102008,
            0x04002200,
            0x04102200,
            0x04002208,
            0x04102208,
            0x04002000,
            0x04102000,
            0x04002008,
            0x04102008,
            0x04002200,
            0x04102200,
            0x04002208,
            0x04102208,
            0x00000000,
            0x00100000,
            0x00000008,
            0x00100008,
            0x00000200,
            0x00100200,
            0x00000208,
            0x00100208,
            0x00000000,
            0x00100000,
            0x00000008,
            0x00100008,
            0x00000200,
            0x00100200,
            0x00000208,
            0x00100208,
            0x04000000,
            0x04100000,
            0x04000008,
            0x04100008,
            0x04000200,
            0x04100200,
            0x04000208,
            0x04100208,
            0x04000000,
            0x04100000,
            0x04000008,
            0x04100008,
            0x04000200,
            0x04100200,
            0x04000208,
            0x04100208,
            0x00002000,
            0x00102000,
            0x00002008,
            0x00102008,
            0x00002200,
            0x00102200,
            0x00002208,
            0x00102208,
            0x00002000,
            0x00102000,
            0x00002008,
            0x00102008,
            0x00002200,
            0x00102200,
            0x00002208,
            0x00102208,
            0x04002000,
            0x04102000,
            0x04002008,
            0x04102008,
            0x04002200,
            0x04102200,
            0x04002208,
            0x04102208,
            0x04002000,
            0x04102000,
            0x04002008,
            0x04102008,
            0x04002200,
            0x04102200,
            0x04002208,
            0x04102208,
            0x00020000,
            0x00120000,
            0x00020008,
            0x00120008,
            0x00020200,
            0x00120200,
            0x00020208,
            0x00120208,
            0x00020000,
            0x00120000,
            0x00020008,
            0x00120008,
            0x00020200,
            0x00120200,
            0x00020208,
            0x00120208,
            0x04020000,
            0x04120000,
            0x04020008,
            0x04120008,
            0x04020200,
            0x04120200,
            0x04020208,
            0x04120208,
            0x04020000,
            0x04120000,
            0x04020008,
            0x04120008,
            0x04020200,
            0x04120200,
            0x04020208,
            0x04120208,
            0x00022000,
            0x00122000,
            0x00022008,
            0x00122008,
            0x00022200,
            0x00122200,
            0x00022208,
            0x00122208,
            0x00022000,
            0x00122000,
            0x00022008,
            0x00122008,
            0x00022200,
            0x00122200,
            0x00022208,
            0x00122208,
            0x04022000,
            0x04122000,
            0x04022008,
            0x04122008,
            0x04022200,
            0x04122200,
            0x04022208,
            0x04122208,
            0x04022000,
            0x04122000,
            0x04022008,
            0x04122008,
            0x04022200,
            0x04122200,
            0x04022208,
            0x04122208,
            0x00020000,
            0x00120000,
            0x00020008,
            0x00120008,
            0x00020200,
            0x00120200,
            0x00020208,
            0x00120208,
            0x00020000,
            0x00120000,
            0x00020008,
            0x00120008,
            0x00020200,
            0x00120200,
            0x00020208,
            0x00120208,
            0x04020000,
            0x04120000,
            0x04020008,
            0x04120008,
            0x04020200,
            0x04120200,
            0x04020208,
            0x04120208,
            0x04020000,
            0x04120000,
            0x04020008,
            0x04120008,
            0x04020200,
            0x04120200,
            0x04020208,
            0x04120208,
            0x00022000,
            0x00122000,
            0x00022008,
            0x00122008,
            0x00022200,
            0x00122200,
            0x00022208,
            0x00122208,
            0x00022000,
            0x00122000,
            0x00022008,
            0x00122008,
            0x00022200,
            0x00122200,
            0x00022208,
            0x00122208,
            0x04022000,
            0x04122000,
            0x04022008,
            0x04122008,
            0x04022200,
            0x04122200,
            0x04022208,
            0x04122208,
            0x04022000,
            0x04122000,
            0x04022008,
            0x04122008,
            0x04022200,
            0x04122200,
            0x04022208,
            0x04122208
        );
        static $pc2mapd1 = array(
            0x00000000,
            0x00000001,
            0x08000000,
            0x08000001,
            0x00200000,
            0x00200001,
            0x08200000,
            0x08200001,
            0x00000002,
            0x00000003,
            0x08000002,
            0x08000003,
            0x00200002,
            0x00200003,
            0x08200002,
            0x08200003
        );
        static $pc2mapd2 = array(
            0x00000000,
            0x00100000,
            0x00000800,
            0x00100800,
            0x00000000,
            0x00100000,
            0x00000800,
            0x00100800,
            0x04000000,
            0x04100000,
            0x04000800,
            0x04100800,
            0x04000000,
            0x04100000,
            0x04000800,
            0x04100800,
            0x00000004,
            0x00100004,
            0x00000804,
            0x00100804,
            0x00000004,
            0x00100004,
            0x00000804,
            0x00100804,
            0x04000004,
            0x04100004,
            0x04000804,
            0x04100804,
            0x04000004,
            0x04100004,
            0x04000804,
            0x04100804,
            0x00000000,
            0x00100000,
            0x00000800,
            0x00100800,
            0x00000000,
            0x00100000,
            0x00000800,
            0x00100800,
            0x04000000,
            0x04100000,
            0x04000800,
            0x04100800,
            0x04000000,
            0x04100000,
            0x04000800,
            0x04100800,
            0x00000004,
            0x00100004,
            0x00000804,
            0x00100804,
            0x00000004,
            0x00100004,
            0x00000804,
            0x00100804,
            0x04000004,
            0x04100004,
            0x04000804,
            0x04100804,
            0x04000004,
            0x04100004,
            0x04000804,
            0x04100804,
            0x00000200,
            0x00100200,
            0x00000A00,
            0x00100A00,
            0x00000200,
            0x00100200,
            0x00000A00,
            0x00100A00,
            0x04000200,
            0x04100200,
            0x04000A00,
            0x04100A00,
            0x04000200,
            0x04100200,
            0x04000A00,
            0x04100A00,
            0x00000204,
            0x00100204,
            0x00000A04,
            0x00100A04,
            0x00000204,
            0x00100204,
            0x00000A04,
            0x00100A04,
            0x04000204,
            0x04100204,
            0x04000A04,
            0x04100A04,
            0x04000204,
            0x04100204,
            0x04000A04,
            0x04100A04,
            0x00000200,
            0x00100200,
            0x00000A00,
            0x00100A00,
            0x00000200,
            0x00100200,
            0x00000A00,
            0x00100A00,
            0x04000200,
            0x04100200,
            0x04000A00,
            0x04100A00,
            0x04000200,
            0x04100200,
            0x04000A00,
            0x04100A00,
            0x00000204,
            0x00100204,
            0x00000A04,
            0x00100A04,
            0x00000204,
            0x00100204,
            0x00000A04,
            0x00100A04,
            0x04000204,
            0x04100204,
            0x04000A04,
            0x04100A04,
            0x04000204,
            0x04100204,
            0x04000A04,
            0x04100A04,
            0x00020000,
            0x00120000,
            0x00020800,
            0x00120800,
            0x00020000,
            0x00120000,
            0x00020800,
            0x00120800,
            0x04020000,
            0x04120000,
            0x04020800,
            0x04120800,
            0x04020000,
            0x04120000,
            0x04020800,
            0x04120800,
            0x00020004,
            0x00120004,
            0x00020804,
            0x00120804,
            0x00020004,
            0x00120004,
            0x00020804,
            0x00120804,
            0x04020004,
            0x04120004,
            0x04020804,
            0x04120804,
            0x04020004,
            0x04120004,
            0x04020804,
            0x04120804,
            0x00020000,
            0x00120000,
            0x00020800,
            0x00120800,
            0x00020000,
            0x00120000,
            0x00020800,
            0x00120800,
            0x04020000,
            0x04120000,
            0x04020800,
            0x04120800,
            0x04020000,
            0x04120000,
            0x04020800,
            0x04120800,
            0x00020004,
            0x00120004,
            0x00020804,
            0x00120804,
            0x00020004,
            0x00120004,
            0x00020804,
            0x00120804,
            0x04020004,
            0x04120004,
            0x04020804,
            0x04120804,
            0x04020004,
            0x04120004,
            0x04020804,
            0x04120804,
            0x00020200,
            0x00120200,
            0x00020A00,
            0x00120A00,
            0x00020200,
            0x00120200,
            0x00020A00,
            0x00120A00,
            0x04020200,
            0x04120200,
            0x04020A00,
            0x04120A00,
            0x04020200,
            0x04120200,
            0x04020A00,
            0x04120A00,
            0x00020204,
            0x00120204,
            0x00020A04,
            0x00120A04,
            0x00020204,
            0x00120204,
            0x00020A04,
            0x00120A04,
            0x04020204,
            0x04120204,
            0x04020A04,
            0x04120A04,
            0x04020204,
            0x04120204,
            0x04020A04,
            0x04120A04,
            0x00020200,
            0x00120200,
            0x00020A00,
            0x00120A00,
            0x00020200,
            0x00120200,
            0x00020A00,
            0x00120A00,
            0x04020200,
            0x04120200,
            0x04020A00,
            0x04120A00,
            0x04020200,
            0x04120200,
            0x04020A00,
            0x04120A00,
            0x00020204,
            0x00120204,
            0x00020A04,
            0x00120A04,
            0x00020204,
            0x00120204,
            0x00020A04,
            0x00120A04,
            0x04020204,
            0x04120204,
            0x04020A04,
            0x04120A04,
            0x04020204,
            0x04120204,
            0x04020A04,
            0x04120A04
        );
        static $pc2mapd3 = array(
            0x00000000,
            0x00010000,
            0x02000000,
            0x02010000,
            0x00000020,
            0x00010020,
            0x02000020,
            0x02010020,
            0x00040000,
            0x00050000,
            0x02040000,
            0x02050000,
            0x00040020,
            0x00050020,
            0x02040020,
            0x02050020,
            0x00002000,
            0x00012000,
            0x02002000,
            0x02012000,
            0x00002020,
            0x00012020,
            0x02002020,
            0x02012020,
            0x00042000,
            0x00052000,
            0x02042000,
            0x02052000,
            0x00042020,
            0x00052020,
            0x02042020,
            0x02052020,
            0x00000000,
            0x00010000,
            0x02000000,
            0x02010000,
            0x00000020,
            0x00010020,
            0x02000020,
            0x02010020,
            0x00040000,
            0x00050000,
            0x02040000,
            0x02050000,
            0x00040020,
            0x00050020,
            0x02040020,
            0x02050020,
            0x00002000,
            0x00012000,
            0x02002000,
            0x02012000,
            0x00002020,
            0x00012020,
            0x02002020,
            0x02012020,
            0x00042000,
            0x00052000,
            0x02042000,
            0x02052000,
            0x00042020,
            0x00052020,
            0x02042020,
            0x02052020,
            0x00000010,
            0x00010010,
            0x02000010,
            0x02010010,
            0x00000030,
            0x00010030,
            0x02000030,
            0x02010030,
            0x00040010,
            0x00050010,
            0x02040010,
            0x02050010,
            0x00040030,
            0x00050030,
            0x02040030,
            0x02050030,
            0x00002010,
            0x00012010,
            0x02002010,
            0x02012010,
            0x00002030,
            0x00012030,
            0x02002030,
            0x02012030,
            0x00042010,
            0x00052010,
            0x02042010,
            0x02052010,
            0x00042030,
            0x00052030,
            0x02042030,
            0x02052030,
            0x00000010,
            0x00010010,
            0x02000010,
            0x02010010,
            0x00000030,
            0x00010030,
            0x02000030,
            0x02010030,
            0x00040010,
            0x00050010,
            0x02040010,
            0x02050010,
            0x00040030,
            0x00050030,
            0x02040030,
            0x02050030,
            0x00002010,
            0x00012010,
            0x02002010,
            0x02012010,
            0x00002030,
            0x00012030,
            0x02002030,
            0x02012030,
            0x00042010,
            0x00052010,
            0x02042010,
            0x02052010,
            0x00042030,
            0x00052030,
            0x02042030,
            0x02052030,
            0x20000000,
            0x20010000,
            0x22000000,
            0x22010000,
            0x20000020,
            0x20010020,
            0x22000020,
            0x22010020,
            0x20040000,
            0x20050000,
            0x22040000,
            0x22050000,
            0x20040020,
            0x20050020,
            0x22040020,
            0x22050020,
            0x20002000,
            0x20012000,
            0x22002000,
            0x22012000,
            0x20002020,
            0x20012020,
            0x22002020,
            0x22012020,
            0x20042000,
            0x20052000,
            0x22042000,
            0x22052000,
            0x20042020,
            0x20052020,
            0x22042020,
            0x22052020,
            0x20000000,
            0x20010000,
            0x22000000,
            0x22010000,
            0x20000020,
            0x20010020,
            0x22000020,
            0x22010020,
            0x20040000,
            0x20050000,
            0x22040000,
            0x22050000,
            0x20040020,
            0x20050020,
            0x22040020,
            0x22050020,
            0x20002000,
            0x20012000,
            0x22002000,
            0x22012000,
            0x20002020,
            0x20012020,
            0x22002020,
            0x22012020,
            0x20042000,
            0x20052000,
            0x22042000,
            0x22052000,
            0x20042020,
            0x20052020,
            0x22042020,
            0x22052020,
            0x20000010,
            0x20010010,
            0x22000010,
            0x22010010,
            0x20000030,
            0x20010030,
            0x22000030,
            0x22010030,
            0x20040010,
            0x20050010,
            0x22040010,
            0x22050010,
            0x20040030,
            0x20050030,
            0x22040030,
            0x22050030,
            0x20002010,
            0x20012010,
            0x22002010,
            0x22012010,
            0x20002030,
            0x20012030,
            0x22002030,
            0x22012030,
            0x20042010,
            0x20052010,
            0x22042010,
            0x22052010,
            0x20042030,
            0x20052030,
            0x22042030,
            0x22052030,
            0x20000010,
            0x20010010,
            0x22000010,
            0x22010010,
            0x20000030,
            0x20010030,
            0x22000030,
            0x22010030,
            0x20040010,
            0x20050010,
            0x22040010,
            0x22050010,
            0x20040030,
            0x20050030,
            0x22040030,
            0x22050030,
            0x20002010,
            0x20012010,
            0x22002010,
            0x22012010,
            0x20002030,
            0x20012030,
            0x22002030,
            0x22012030,
            0x20042010,
            0x20052010,
            0x22042010,
            0x22052010,
            0x20042030,
            0x20052030,
            0x22042030,
            0x22052030
        );
        static $pc2mapd4 = array(
            0x00000000,
            0x00000400,
            0x01000000,
            0x01000400,
            0x00000000,
            0x00000400,
            0x01000000,
            0x01000400,
            0x00000100,
            0x00000500,
            0x01000100,
            0x01000500,
            0x00000100,
            0x00000500,
            0x01000100,
            0x01000500,
            0x10000000,
            0x10000400,
            0x11000000,
            0x11000400,
            0x10000000,
            0x10000400,
            0x11000000,
            0x11000400,
            0x10000100,
            0x10000500,
            0x11000100,
            0x11000500,
            0x10000100,
            0x10000500,
            0x11000100,
            0x11000500,
            0x00080000,
            0x00080400,
            0x01080000,
            0x01080400,
            0x00080000,
            0x00080400,
            0x01080000,
            0x01080400,
            0x00080100,
            0x00080500,
            0x01080100,
            0x01080500,
            0x00080100,
            0x00080500,
            0x01080100,
            0x01080500,
            0x10080000,
            0x10080400,
            0x11080000,
            0x11080400,
            0x10080000,
            0x10080400,
            0x11080000,
            0x11080400,
            0x10080100,
            0x10080500,
            0x11080100,
            0x11080500,
            0x10080100,
            0x10080500,
            0x11080100,
            0x11080500,
            0x00000008,
            0x00000408,
            0x01000008,
            0x01000408,
            0x00000008,
            0x00000408,
            0x01000008,
            0x01000408,
            0x00000108,
            0x00000508,
            0x01000108,
            0x01000508,
            0x00000108,
            0x00000508,
            0x01000108,
            0x01000508,
            0x10000008,
            0x10000408,
            0x11000008,
            0x11000408,
            0x10000008,
            0x10000408,
            0x11000008,
            0x11000408,
            0x10000108,
            0x10000508,
            0x11000108,
            0x11000508,
            0x10000108,
            0x10000508,
            0x11000108,
            0x11000508,
            0x00080008,
            0x00080408,
            0x01080008,
            0x01080408,
            0x00080008,
            0x00080408,
            0x01080008,
            0x01080408,
            0x00080108,
            0x00080508,
            0x01080108,
            0x01080508,
            0x00080108,
            0x00080508,
            0x01080108,
            0x01080508,
            0x10080008,
            0x10080408,
            0x11080008,
            0x11080408,
            0x10080008,
            0x10080408,
            0x11080008,
            0x11080408,
            0x10080108,
            0x10080508,
            0x11080108,
            0x11080508,
            0x10080108,
            0x10080508,
            0x11080108,
            0x11080508,
            0x00001000,
            0x00001400,
            0x01001000,
            0x01001400,
            0x00001000,
            0x00001400,
            0x01001000,
            0x01001400,
            0x00001100,
            0x00001500,
            0x01001100,
            0x01001500,
            0x00001100,
            0x00001500,
            0x01001100,
            0x01001500,
            0x10001000,
            0x10001400,
            0x11001000,
            0x11001400,
            0x10001000,
            0x10001400,
            0x11001000,
            0x11001400,
            0x10001100,
            0x10001500,
            0x11001100,
            0x11001500,
            0x10001100,
            0x10001500,
            0x11001100,
            0x11001500,
            0x00081000,
            0x00081400,
            0x01081000,
            0x01081400,
            0x00081000,
            0x00081400,
            0x01081000,
            0x01081400,
            0x00081100,
            0x00081500,
            0x01081100,
            0x01081500,
            0x00081100,
            0x00081500,
            0x01081100,
            0x01081500,
            0x10081000,
            0x10081400,
            0x11081000,
            0x11081400,
            0x10081000,
            0x10081400,
            0x11081000,
            0x11081400,
            0x10081100,
            0x10081500,
            0x11081100,
            0x11081500,
            0x10081100,
            0x10081500,
            0x11081100,
            0x11081500,
            0x00001008,
            0x00001408,
            0x01001008,
            0x01001408,
            0x00001008,
            0x00001408,
            0x01001008,
            0x01001408,
            0x00001108,
            0x00001508,
            0x01001108,
            0x01001508,
            0x00001108,
            0x00001508,
            0x01001108,
            0x01001508,
            0x10001008,
            0x10001408,
            0x11001008,
            0x11001408,
            0x10001008,
            0x10001408,
            0x11001008,
            0x11001408,
            0x10001108,
            0x10001508,
            0x11001108,
            0x11001508,
            0x10001108,
            0x10001508,
            0x11001108,
            0x11001508,
            0x00081008,
            0x00081408,
            0x01081008,
            0x01081408,
            0x00081008,
            0x00081408,
            0x01081008,
            0x01081408,
            0x00081108,
            0x00081508,
            0x01081108,
            0x01081508,
            0x00081108,
            0x00081508,
            0x01081108,
            0x01081508,
            0x10081008,
            0x10081408,
            0x11081008,
            0x11081408,
            0x10081008,
            0x10081408,
            0x11081008,
            0x11081408,
            0x10081108,
            0x10081508,
            0x11081108,
            0x11081508,
            0x10081108,
            0x10081508,
            0x11081108,
            0x11081508
        );
        
        // pad the key and remove extra characters as appropriate.
        $key = str_pad(substr($key, 0, 8), 8, chr(0));
        
        // Perform the PC/1 transformation and compute C and D.
        $t = unpack('Nl/Nr', $key);
        list ($l, $r) = array(
            $t['l'],
            $t['r']
        );
        $key = ($this->shuffle[$pc1map[$r & 0xFF]] & "\x80\x80\x80\x80\x80\x80\x80\x00") | ($this->shuffle[$pc1map[($r >> 8) & 0xFF]] & "\x40\x40\x40\x40\x40\x40\x40\x00") | ($this->shuffle[$pc1map[($r >> 16) & 0xFF]] & "\x20\x20\x20\x20\x20\x20\x20\x00") | ($this->shuffle[$pc1map[($r >> 24) & 0xFF]] & "\x10\x10\x10\x10\x10\x10\x10\x00") | ($this->shuffle[$pc1map[$l & 0xFF]] & "\x08\x08\x08\x08\x08\x08\x08\x00") | ($this->shuffle[$pc1map[($l >> 8) & 0xFF]] & "\x04\x04\x04\x04\x04\x04\x04\x00") | ($this->shuffle[$pc1map[($l >> 16) & 0xFF]] & "\x02\x02\x02\x02\x02\x02\x02\x00") | ($this->shuffle[$pc1map[($l >> 24) & 0xFF]] & "\x01\x01\x01\x01\x01\x01\x01\x00");
        $key = unpack('Nc/Nd', $key);
        $c = ($key['c'] >> 4) & 0x0FFFFFFF;
        $d = (($key['d'] >> 4) & 0x0FFFFFF0) | ($key['c'] & 0x0F);
        
        $keys = array();
        for ($i = 0; $i < 16; $i ++) {
            $c <<= $shifts[$i];
            $c = ($c | ($c >> 28)) & 0x0FFFFFFF;
            $d <<= $shifts[$i];
            $d = ($d | ($d >> 28)) & 0x0FFFFFFF;
            
            // Perform the PC-2 transformation.
            $cp = $pc2mapc1[$c >> 24] | $pc2mapc2[($c >> 16) & 0xFF] | $pc2mapc3[($c >> 8) & 0xFF] | $pc2mapc4[$c & 0xFF];
            $dp = $pc2mapd1[$d >> 24] | $pc2mapd2[($d >> 16) & 0xFF] | $pc2mapd3[($d >> 8) & 0xFF] | $pc2mapd4[$d & 0xFF];
            
            // Reorder: odd bytes/even bytes. Push the result in key schedule.
            $keys[] = array(
                ($cp & 0xFF000000) | (($cp << 8) & 0x00FF0000) | (($dp >> 16) & 0x0000FF00) | (($dp >> 8) & 0x000000FF),
                (($cp << 8) & 0xFF000000) | (($cp << 16) & 0x00FF0000) | (($dp >> 8) & 0x0000FF00) | ($dp & 0x000000FF)
            );
        }
        
        $keys = array(
            CRYPT_DES_ENCRYPT => $keys,
            CRYPT_DES_DECRYPT => array_reverse($keys),
            CRYPT_DES_ENCRYPT_1DIM => array(),
            CRYPT_DES_DECRYPT_1DIM => array()
        );
        
        // Generate 1-dim arrays for inline en/decrypting
        for ($i = 0; $i < 16; ++ $i) {
            $keys[CRYPT_DES_ENCRYPT_1DIM][] = $keys[CRYPT_DES_ENCRYPT][$i][0];
            $keys[CRYPT_DES_ENCRYPT_1DIM][] = $keys[CRYPT_DES_ENCRYPT][$i][1];
            $keys[CRYPT_DES_DECRYPT_1DIM][] = $keys[CRYPT_DES_DECRYPT][$i][0];
            $keys[CRYPT_DES_DECRYPT_1DIM][] = $keys[CRYPT_DES_DECRYPT][$i][1];
        }
        
        return $keys;
    }

    /**
     * String Shift
     *
     * Inspired by array_shift
     *
     * @param String $string            
     * @return String
     * @access private
     */
    function _string_shift(&$string)
    {
        $substr = substr($string, 0, 8);
        $string = substr($string, 8);
        return $substr;
    }

    /**
     * Creates performance-optimized function for de/encrypt(), storing it in $this->inline_crypt
     *
     * @param
     *            optional Integer $des_rounds (1 = DES[default], 3 = TribleDES)
     * @access private
     */
    function inline_crypt_setup($des_rounds = 1)
    {
        $lambda_functions = & Crypt_DES::get_lambda_functions();
        $block_size = 8;
        $mode = $this->mode;
        
        $code_hash = "$mode,$des_rounds";
        
        if (!isset($lambda_functions[$code_hash])) {
            // Generating encrypt code:
            $ki = - 1;
            $init_cryptBlock = '
                $shuffle  = $self->shuffle;
                $invipmap = $self->invipmap;
                $ipmap = $self->ipmap;
                $sbox1 = $self->sbox1;
                $sbox2 = $self->sbox2;
                $sbox3 = $self->sbox3;
                $sbox4 = $self->sbox4;
                $sbox5 = $self->sbox5;
                $sbox6 = $self->sbox6;
                $sbox7 = $self->sbox7;
                $sbox8 = $self->sbox8;
            ';
            
            $_cryptBlock = '$in = unpack("N*", $in);' . "\n";
            for ($des_round = 0; $des_round < $des_rounds; ++ $des_round) {
                // Do the initial IP permutation.
                $_cryptBlock .= '
                    $l  = $in[1];
                    $r  = $in[2];
                    $in = unpack("N*",
                        ($shuffle[$ipmap[ $r        & 0xFF]] & "\x80\x80\x80\x80\x80\x80\x80\x80") |
                        ($shuffle[$ipmap[($r >>  8) & 0xFF]] & "\x40\x40\x40\x40\x40\x40\x40\x40") |
                        ($shuffle[$ipmap[($r >> 16) & 0xFF]] & "\x20\x20\x20\x20\x20\x20\x20\x20") |
                        ($shuffle[$ipmap[($r >> 24) & 0xFF]] & "\x10\x10\x10\x10\x10\x10\x10\x10") |
                        ($shuffle[$ipmap[ $l        & 0xFF]] & "\x08\x08\x08\x08\x08\x08\x08\x08") |
                        ($shuffle[$ipmap[($l >>  8) & 0xFF]] & "\x04\x04\x04\x04\x04\x04\x04\x04") |
                        ($shuffle[$ipmap[($l >> 16) & 0xFF]] & "\x02\x02\x02\x02\x02\x02\x02\x02") |
                        ($shuffle[$ipmap[($l >> 24) & 0xFF]] & "\x01\x01\x01\x01\x01\x01\x01\x01")
                    );

                    ' . '' /* Extract L0 and R0 */ . '
                    $l = $in[1];
                    $r = $in[2];
                ';
                
                // Perform the 16 steps.
                // start of "the Feistel (F) function" - see the following URL:
                // http://en.wikipedia.org/wiki/Image:Data_Encryption_Standard_InfoBox_Diagram.png
                // Merge key schedule.
                for ($i = 0; $i < 8; ++ $i) {
                    $_cryptBlock .= '
                        $b1 = (($r >>  3) & 0x1FFFFFFF)  ^ ($r << 29) ^ $k_' . (++ $ki) . ';
                        $b2 = (($r >> 31) & 0x00000001)  ^ ($r <<  1) ^ $k_' . (++ $ki) . ';
                        $l  = $sbox1[($b1 >> 24) & 0x3F] ^ $sbox2[($b2 >> 24) & 0x3F] ^
                              $sbox3[($b1 >> 16) & 0x3F] ^ $sbox4[($b2 >> 16) & 0x3F] ^
                              $sbox5[($b1 >>  8) & 0x3F] ^ $sbox6[($b2 >>  8) & 0x3F] ^
                              $sbox7[ $b1        & 0x3F] ^ $sbox8[ $b2        & 0x3F] ^ $l;

                        $b1 = (($l >>  3) & 0x1FFFFFFF)  ^ ($l << 29) ^ $k_' . (++ $ki) . ';
                        $b2 = (($l >> 31) & 0x00000001)  ^ ($l <<  1) ^ $k_' . (++ $ki) . ';
                        $r  = $sbox1[($b1 >> 24) & 0x3F] ^ $sbox2[($b2 >> 24) & 0x3F] ^
                              $sbox3[($b1 >> 16) & 0x3F] ^ $sbox4[($b2 >> 16) & 0x3F] ^
                              $sbox5[($b1 >>  8) & 0x3F] ^ $sbox6[($b2 >>  8) & 0x3F] ^
                              $sbox7[ $b1        & 0x3F] ^ $sbox8[ $b2        & 0x3F] ^ $r;
                    ';
                }
                
                // Perform the inverse IP permutation.
                $_cryptBlock .= '$in = ' . ($des_round == $des_rounds - 1 ? '(' : 'unpack("N*",') . '
                        ($shuffle[$invipmap[($l >> 24) & 0xFF]] & "\x80\x80\x80\x80\x80\x80\x80\x80") |
                        ($shuffle[$invipmap[($r >> 24) & 0xFF]] & "\x40\x40\x40\x40\x40\x40\x40\x40") |
                        ($shuffle[$invipmap[($l >> 16) & 0xFF]] & "\x20\x20\x20\x20\x20\x20\x20\x20") |
                        ($shuffle[$invipmap[($r >> 16) & 0xFF]] & "\x10\x10\x10\x10\x10\x10\x10\x10") |
                        ($shuffle[$invipmap[($l >>  8) & 0xFF]] & "\x08\x08\x08\x08\x08\x08\x08\x08") |
                        ($shuffle[$invipmap[($r >>  8) & 0xFF]] & "\x04\x04\x04\x04\x04\x04\x04\x04") |
                        ($shuffle[$invipmap[ $l        & 0xFF]] & "\x02\x02\x02\x02\x02\x02\x02\x02") |
                        ($shuffle[$invipmap[ $r        & 0xFF]] & "\x01\x01\x01\x01\x01\x01\x01\x01")
                    );
                ';
            }
            
            // Generating mode of operation code:
            switch ($mode) {
                case CRYPT_DES_MODE_ECB:
                    $encrypt = $init_cryptBlock . '
                        extract($self->keys[CRYPT_DES_ENCRYPT_1DIM],  EXTR_PREFIX_ALL, "k");
                        $ciphertext = "";
                        $plaintext_len = strlen($text);

                        for ($i = 0; $i < $plaintext_len; $i+= ' . $block_size . ') {
                            $in = substr($text, $i, ' . $block_size . ');
                            ' . $_cryptBlock . '
                            $ciphertext.= $in;
                        }
                       
                        return $ciphertext;
                        ';
                    
                    $decrypt = $init_cryptBlock . '
                        extract($self->keys[CRYPT_DES_DECRYPT_1DIM],  EXTR_PREFIX_ALL, "k");
                        $plaintext = "";
                        $ciphertext_len = strlen($text);

                        for ($i = 0; $i < $ciphertext_len; $i+= ' . $block_size . ') {
                            $in = substr($text, $i, ' . $block_size . ');
                            ' . $_cryptBlock . '
                            $plaintext.= $in;
                        }

                        return $self->_unpad($plaintext);
                        ';
                    break;
                case CRYPT_DES_MODE_CBC:
                    $encrypt = $init_cryptBlock . '
                        extract($self->keys[CRYPT_DES_ENCRYPT_1DIM],  EXTR_PREFIX_ALL, "k");
                        $ciphertext = "";
                        $plaintext_len = strlen($text);

                        $in = $self->encryptIV;

                        for ($i = 0; $i < $plaintext_len; $i+= ' . $block_size . ') {
                            $in = substr($text, $i, ' . $block_size . ') ^ $in;
                            ' . $_cryptBlock . '
                            $ciphertext.= $in;
                        }

                        if ($self->continuousBuffer) {
                            $self->encryptIV = $in;
                        }

                        return $ciphertext;
                        ';
                    
                    $decrypt = $init_cryptBlock . '
                        extract($self->keys[CRYPT_DES_DECRYPT_1DIM],  EXTR_PREFIX_ALL, "k");
                        $plaintext = "";
                        $ciphertext_len = strlen($text);

                        $iv = $self->decryptIV;

                        for ($i = 0; $i < $ciphertext_len; $i+= ' . $block_size . ') {
                            $in = $block = substr($text, $i, ' . $block_size . ');
                            ' . $_cryptBlock . '
                            $plaintext.= $in ^ $iv;
                            $iv = $block;
                        }

                        if ($self->continuousBuffer) {
                            $self->decryptIV = $iv;
                        }

                        return $self->_unpad($plaintext);
                        ';
                    break;
                case CRYPT_DES_MODE_CTR:
                    $encrypt = $init_cryptBlock . '
                        extract($self->keys[CRYPT_DES_ENCRYPT_1DIM],  EXTR_PREFIX_ALL, "k");
                        $ciphertext = "";
                        $plaintext_len = strlen($text);
                        $xor = $self->encryptIV;
                        $buffer = &$self->enbuffer;

                        if (strlen($buffer["encrypted"])) {
                            for ($i = 0; $i < $plaintext_len; $i+= ' . $block_size . ') {
                                $block = substr($text, $i, ' . $block_size . ');
                                if (strlen($block) > strlen($buffer["encrypted"])) {
                                    $in = $self->_generate_xor($xor);
                                    ' . $_cryptBlock . '
                                    $buffer["encrypted"].= $in;
                                }
                                $key = $self->_string_shift($buffer["encrypted"]);
                                $ciphertext.= $block ^ $key;
                            }
                        } else {
                            for ($i = 0; $i < $plaintext_len; $i+= ' . $block_size . ') {
                                $block = substr($text, $i, ' . $block_size . ');
                                $in = $self->_generate_xor($xor);
                                ' . $_cryptBlock . '
                                $key = $in;
                                $ciphertext.= $block ^ $key;
                            }
                        }
                        if ($self->continuousBuffer) {
                            $self->encryptIV = $xor;
                            if ($start = $plaintext_len % ' . $block_size . ') {
                                $buffer["encrypted"] = substr($key, $start) . $buffer["encrypted"];
                            }
                        }

                        return $ciphertext;
                    ';
                    
                    $decrypt = $init_cryptBlock . '
                        extract($self->keys[CRYPT_DES_ENCRYPT_1DIM],  EXTR_PREFIX_ALL, "k");
                        $plaintext = "";
                        $ciphertext_len = strlen($text);
                        $xor = $self->decryptIV;
                        $buffer = &$self->debuffer;

                        if (strlen($buffer["ciphertext"])) {
                            for ($i = 0; $i < $ciphertext_len; $i+= ' . $block_size . ') {
                                $block = substr($text, $i, ' . $block_size . ');
                                if (strlen($block) > strlen($buffer["ciphertext"])) {
                                    $in = $self->_generate_xor($xor);
                                    ' . $_cryptBlock . '
                                    $buffer["ciphertext"].= $in;
                                }
                                $key = $self->_string_shift($buffer["ciphertext"]);
                                $plaintext.= $block ^ $key;
                            }
                        } else {
                            for ($i = 0; $i < $ciphertext_len; $i+= ' . $block_size . ') {
                                $block = substr($text, $i, ' . $block_size . ');
                                $in = $self->_generate_xor($xor);
                                ' . $_cryptBlock . '
                                $key = $in;
                                $plaintext.= $block ^ $key;
                            }
                        }
                        if ($self->continuousBuffer) {
                            $self->decryptIV = $xor;
                            if ($start = $ciphertext_len % ' . $block_size . ') {
                                $buffer["ciphertext"] = substr($key, $start) . $buffer["ciphertext"];
                            }
                        }
                       
                        return $plaintext;
                        ';
                    break;
                case CRYPT_DES_MODE_CFB:
                    $encrypt = $init_cryptBlock . '
                        extract($self->keys[CRYPT_DES_ENCRYPT_1DIM],  EXTR_PREFIX_ALL, "k");
                        $ciphertext = "";
                        $buffer = &$self->enbuffer;

                        if ($self->continuousBuffer) {
                            $iv = &$self->encryptIV;
                            $pos = &$buffer["pos"];
                        } else {
                            $iv = $self->encryptIV;
                            $pos = 0;
                        }
                        $len = strlen($text);
                        $i = 0;
                        if ($pos) {
                            $orig_pos = $pos;
                            $max = ' . $block_size . ' - $pos;
                            if ($len >= $max) {
                                $i = $max;
                                $len-= $max;
                                $pos = 0;
                            } else {
                                $i = $len;
                                $pos+= $len;
                                $len = 0;
                            }
                            $ciphertext = substr($iv, $orig_pos) ^ $text;
                            $iv = substr_replace($iv, $ciphertext, $orig_pos, $i);
                        }
                        while ($len >= ' . $block_size . ') {
                            $in = $iv;
                            ' . $_cryptBlock . ';
                            $iv = $in ^ substr($text, $i, ' . $block_size . ');
                            $ciphertext.= $iv;
                            $len-= ' . $block_size . ';
                            $i+= ' . $block_size . ';
                        }
                        if ($len) {
                            $in = $iv;
                            ' . $_cryptBlock . '
                            $iv = $in;
                            $block = $iv ^ substr($text, $i);
                            $iv = substr_replace($iv, $block, 0, $len);
                            $ciphertext.= $block;
                            $pos = $len;
                        }
                        return $ciphertext;
                    ';
                    
                    $decrypt = $init_cryptBlock . '
                        extract($self->keys[CRYPT_DES_ENCRYPT_1DIM],  EXTR_PREFIX_ALL, "k");
                        $plaintext = "";
                        $buffer = &$self->debuffer;

                        if ($self->continuousBuffer) {
                            $iv = &$self->decryptIV;
                            $pos = &$buffer["pos"];
                        } else {
                            $iv = $self->decryptIV;
                            $pos = 0;
                        }
                        $len = strlen($text);
                        $i = 0;
                        if ($pos) {
                            $orig_pos = $pos;
                            $max = ' . $block_size . ' - $pos;
                            if ($len >= $max) {
                                $i = $max;
                                $len-= $max;
                                $pos = 0;
                            } else {
                                $i = $len;
                                $pos+= $len;
                                $len = 0;
                            }
                            $plaintext = substr($iv, $orig_pos) ^ $text;
                            $iv = substr_replace($iv, substr($text, 0, $i), $orig_pos, $i);
                        }
                        while ($len >= ' . $block_size . ') {
                            $in = $iv;
                            ' . $_cryptBlock . '
                            $iv = $in;
                            $cb = substr($text, $i, ' . $block_size . ');
                            $plaintext.= $iv ^ $cb;
                            $iv = $cb;
                            $len-= ' . $block_size . ';
                            $i+= ' . $block_size . ';
                        }
                        if ($len) {
                            $in = $iv;
                            ' . $_cryptBlock . '
                            $iv = $in;
                            $plaintext.= $iv ^ substr($text, $i);
                            $iv = substr_replace($iv, substr($text, $i), 0, $len);
                            $pos = $len;
                        }

                        return $plaintext;
                        ';
                    break;
                case CRYPT_DES_MODE_OFB:
                    $encrypt = $init_cryptBlock . '
                        extract($self->keys[CRYPT_DES_ENCRYPT_1DIM],  EXTR_PREFIX_ALL, "k");
                        $ciphertext = "";
                        $plaintext_len = strlen($text);
                        $xor = $self->encryptIV;
                        $buffer = &$self->enbuffer;

                        if (strlen($buffer["xor"])) {
                            for ($i = 0; $i < $plaintext_len; $i+= ' . $block_size . ') {
                                $block = substr($text, $i, ' . $block_size . ');
                                if (strlen($block) > strlen($buffer["xor"])) {
                                    $in = $xor;
                                    ' . $_cryptBlock . '
                                    $xor = $in;
                                    $buffer["xor"].= $xor;
                                }
                                $key = $self->_string_shift($buffer["xor"]);
                                $ciphertext.= $block ^ $key;
                            }
                        } else {
                            for ($i = 0; $i < $plaintext_len; $i+= ' . $block_size . ') {
                                $in = $xor;
                                ' . $_cryptBlock . '
                                $xor = $in;
                                $ciphertext.= substr($text, $i, ' . $block_size . ') ^ $xor;
                            }
                            $key = $xor;
                        }
                        if ($self->continuousBuffer) {
                            $self->encryptIV = $xor;
                            if ($start = $plaintext_len % ' . $block_size . ') {
                                 $buffer["xor"] = substr($key, $start) . $buffer["xor"];
                            }
                        }
                        return $ciphertext;
                        ';
                    
                    $decrypt = $init_cryptBlock . '
                        extract($self->keys[CRYPT_DES_ENCRYPT_1DIM],  EXTR_PREFIX_ALL, "k");
                        $plaintext = "";
                        $ciphertext_len = strlen($text);
                        $xor = $self->decryptIV;
                        $buffer = &$self->debuffer;

                        if (strlen($buffer["xor"])) {
                            for ($i = 0; $i < $ciphertext_len; $i+= ' . $block_size . ') {
                                $block = substr($text, $i, ' . $block_size . ');
                                if (strlen($block) > strlen($buffer["xor"])) {
                                    $in = $xor;
                                    ' . $_cryptBlock . '
                                    $xor = $in;
                                    $buffer["xor"].= $xor;
                                }
                                $key = $self->_string_shift($buffer["xor"]);
                                $plaintext.= $block ^ $key;
                            }
                        } else {
                            for ($i = 0; $i < $ciphertext_len; $i+= ' . $block_size . ') {
                                $in = $xor;
                                ' . $_cryptBlock . '
                                $xor = $in;
                                $plaintext.= substr($text, $i, ' . $block_size . ') ^ $xor;
                            }
                            $key = $xor;
                        }
                        if ($self->continuousBuffer) {
                            $self->decryptIV = $xor;
                            if ($start = $ciphertext_len % ' . $block_size . ') {
                                 $buffer["xor"] = substr($key, $start) . $buffer["xor"];
                            }
                        }
                        return $plaintext;
                        ';
                    break;
            }
            $lambda_functions[$code_hash] = create_function('$action, &$self, $text', 'if ($action == "encrypt") { ' . $encrypt . ' } else { ' . $decrypt . ' }');
        }
        $this->inline_crypt = $lambda_functions[$code_hash];
    }

    /**
     * Holds the lambda_functions table (classwide)
     *
     * @see inline_crypt_setup()
     * @return Array
     * @access private
     */
    function &get_lambda_functions()
    {
        static $functions = array();
        return $functions;
    }
}

// vim: ts=4:sw=4:et:
// vim6: fdl=1:
