code:
<?php

/**
 * Wrapper around hash() and hash_hmac() functions supporting truncated hashes
 * such as sha256-96.  Any hash algorithm returned by hash_algos() (and
 * truncated versions thereof) are supported.
 *
 * If {@link self::setKey() setKey()} is called, {@link self::hash() hash()} will
 * return the HMAC as opposed to the hash.
 *
 * Here's a short example of how to use this library:
 * <code>
 * <?php
 *    include 'vendor/autoload.php';
 *
 *    $hash = new \phpseclib\Crypt\Hash('sha512');
 *
 *    $hash->setKey('abcdefg');
 *
 *    echo base64_encode($hash->hash('abcdefg'));
 * ?>
 * </code>
 *
 * @category  Crypt
 * @package   Hash
 * @author    Jim Wigginton <terrafrost@php.net>
 * @copyright 2015 Jim Wigginton
 * @author    Andreas Fischer <bantu@phpbb.com>
 * @copyright 2015 Andreas Fischer
 * @license   http://www.opensource.org/licenses/mit-license.html  MIT License
 * @link      http://phpseclib.sourceforge.net
 */

namespace phpseclib\Crypt;

use phpseclib\Math\BigInteger;
use phpseclib\Exception\UnsupportedAlgorithmException;

/**
 * @package Hash
 * @author  Jim Wigginton <terrafrost@php.net>
 * @author  Andreas Fischer <bantu@phpbb.com>
 * @access  public
 */
class Hash
{
    /**
     * Hash Parameter
     *
     * @see self::setHash()
     * @var int
     * @access private
     */
    var $hashParam;

    /**
     * Byte-length of hash output (Internal HMAC)
     *
     * @see self::setHash()
     * @var int
     * @access private
     */
    var $length;

    /**
     * Hash Algorithm
     *
     * @see self::setHash()
     * @var string
     * @access private
     */
    var $hash;

    /**
     * Key
     *
     * @see self::setKey()
     * @var string
     * @access private
     */
    var $key = false;

    /**
     * Initial Hash
     *
     * Used only for sha512/*
     *
     * @see self::_sha512()
     * @var array
     * @access private
     */
    var $initial = false;

    /**
     * Outer XOR (Internal HMAC)
     *
     * Used only for sha512/*
     *
     * @see self::hash()
     * @var string
     * @access private
     */
    var $opad;

    /**
     * Inner XOR (Internal HMAC)
     *
     * Used only for sha512/*
     *
     * @see self::hash()
     * @var string
     * @access private
     */
    var $ipad;

    /**
     * Default Constructor.
     *
     * @param string $hash
     * @access public
     */
    function __construct($hash = 'sha256')
    {
        $this->setHash($hash);

        $this->ipad = str_repeat(chr(0x36), 128);
        $this->opad = str_repeat(chr(0x5C), 128);
    }

    /**
     * Sets the key for HMACs
     *
     * Keys can be of any length.
     *
     * @access public
     * @param string $key
     */
    function setKey($key = false)
    {
        $this->key = $key;
    }

    /**
     * Gets the hash function.
     *
     * As set by the constructor or by the setHash() method.
     *
     * @access public
     * @return string
     */
    function getHash()
    {
        return $this->hashParam;
    }

    /**
     * Sets the hash function.
     *
     * @access public
     * @param string $hash
     */
    function setHash($hash)
    {
        $this->hashParam = $hash = strtolower($hash);
        switch ($hash) {
            case 'md2-96':
            case 'md5-96':
            case 'sha1-96':
            case 'sha256-96':
            case 'sha512-96':
            case 'sha512/224-96':
            case 'sha512/256-96':
                $hash = substr($hash, 0, -3);
                $this->length = 12; // 96 / 8 = 12
                break;
            case 'md2':
            case 'md5':
                $this->length = 16;
                break;
            case 'sha1':
                $this->length = 20;
                break;
            case 'sha224':
            case 'sha512/224':
                $this->length = 28;
                break;
            case 'sha256':
            case 'sha512/256':
                $this->length = 32;
                break;
            case 'sha384':
                $this->length = 48;
                break;
            case 'sha512':
                $this->length = 64;
                break;
            default:
                // see if the hash isn't "officially" supported see if it can
                // be "unofficially" supported and calculate the length
                // accordingly.
                if (in_array($hash, hash_algos())) {
                    $this->length = strlen(hash($hash, '', true));
                    break;
                }
                // if the hash algorithm doens't exist maybe it's a truncated
                // hash, e.g. whirlpool-12 or some such.
                if (preg_match('#(-\d+)$#', $hash, $matches)) {
                    $hash = substr($hash, 0, -strlen($matches[1]));
                    if (in_array($hash, hash_algos())) {
                        $this->length = abs($matches[1]) >> 3;
                        break;
                    }
                }
                throw new UnsupportedAlgorithmException(
                    "$hash is not a supported algorithm"
                );
        }

        if ($hash == 'sha512/224' || $hash == 'sha512/256') {
            // from http://csrc.nist.gov/publications/fips/fips180-4/fips-180-4.pdf#page=24
            $this->initial = $hash == 'sha512/256' ?
                array(
                    '22312194FC2BF72C', '9F555FA3C84C64C2', '2393B86B6F53B151', '963877195940EABD',
                    '96283EE2A88EFFE3', 'BE5E1E2553863992', '2B0199FC2C85B8AA', '0EB72DDC81C52CA2'
                ) :
                array(
                    '8C3D37C819544DA2', '73E1996689DCD4D6', '1DFAB7AE32FF9C82', '679DD514582F9FCF',
                    '0F6D2B697BD44DA8', '77E36F7304C48942', '3F9D85A86A1D36C8', '1112E6AD91D692A1'
                );
            for ($i = 0; $i < 8; $i++) {
                $this->initial[$i] = new BigInteger($this->initial[$i], 16);
                $this->initial[$i]->setPrecision(64);
            }
        }

        $this->hash = $hash;
    }

    /**
     * Compute the HMAC.
     *
     * @access public
     * @param string $text
     * @return string
     */
    function hash($text)
    {
        switch ($this->hash) {
            case 'sha512/224':
            case 'sha512/256':
                if (empty($this->key) || !is_string($this->key)) {
                    return substr(self::_sha512($text, $this->initial), 0, $this->length);
                }
                /* "Applications that use keys longer than B bytes will first hash the key using H and then use the
                    resultant L byte string as the actual key to HMAC."

                    -- http://tools.ietf.org/html/rfc2104#section-2 */
                $key = strlen($this->key) > $this->b ? self::_sha512($this->key, $this->initial) : $this->key;

                $key    = str_pad($this->key, 128, chr(0));       // step 1
                $temp   = $this->ipad ^ $this->key;               // step 2
                $temp  .= $text;                                  // step 3
                $temp   = self::_sha512($temp, $this->initial);   // step 4
                $output = $this->opad ^ $this->key;               // step 5
                $output.= $temp;                                  // step 6
                $output = self::_sha512($output, $this->initial); // step 7

                return substr($output, 0, $this->length);
        }
        $output = !empty($this->key) || is_string($this->key) ?
            hash_hmac($this->hash, $text, $this->key, true) :
            hash($this->hash, $text, true);

        return strlen($output) > $this->length
            ? substr($output, 0, $this->length)
            : $output;
    }

    /**
     * Returns the hash length (in bytes)
     *
     * @access public
     * @return int
     */
    function getLength()
    {
        return $this->length;
    }

    /**
     * Pure-PHP implementation of SHA512
     *
     * @access private
     * @param string $m
     */
    static function _sha512($m, $hash)
    {
        static $k;

        if (!isset($k)) {
            // Initialize table of round constants
            // (first 64 bits of the fractional parts of the cube roots of the first 80 primes 2..409)
            $k = array(
                '428a2f98d728ae22', '7137449123ef65cd', 'b5c0fbcfec4d3b2f', 'e9b5dba58189dbbc',
                '3956c25bf348b538', '59f111f1b605d019', '923f82a4af194f9b', 'ab1c5ed5da6d8118',
                'd807aa98a3030242', '12835b0145706fbe', '243185be4ee4b28c', '550c7dc3d5ffb4e2',
                '72be5d74f27b896f', '80deb1fe3b1696b1', '9bdc06a725c71235', 'c19bf174cf692694',
                'e49b69c19ef14ad2', 'efbe4786384f25e3', '0fc19dc68b8cd5b5', '240ca1cc77ac9c65',
                '2de92c6f592b0275', '4a7484aa6ea6e483', '5cb0a9dcbd41fbd4', '76f988da831153b5',
                '983e5152ee66dfab', 'a831c66d2db43210', 'b00327c898fb213f', 'bf597fc7beef0ee4',
                'c6e00bf33da88fc2', 'd5a79147930aa725', '06ca6351e003826f', '142929670a0e6e70',
                '27b70a8546d22ffc', '2e1b21385c26c926', '4d2c6dfc5ac42aed', '53380d139d95b3df',
                '650a73548baf63de', '766a0abb3c77b2a8', '81c2c92e47edaee6', '92722c851482353b',
                'a2bfe8a14cf10364', 'a81a664bbc423001', 'c24b8b70d0f89791', 'c76c51a30654be30',
                'd192e819d6ef5218', 'd69906245565a910', 'f40e35855771202a', '106aa07032bbd1b8',
                '19a4c116b8d2d0c8', '1e376c085141ab53', '2748774cdf8eeb99', '34b0bcb5e19b48a8',
                '391c0cb3c5c95a63', '4ed8aa4ae3418acb', '5b9cca4f7763e373', '682e6ff3d6b2b8a3',
                '748f82ee5defb2fc', '78a5636f43172f60', '84c87814a1f0ab72', '8cc702081a6439ec',
                '90befffa23631e28', 'a4506cebde82bde9', 'bef9a3f7b2c67915', 'c67178f2e372532b',
                'ca273eceea26619c', 'd186b8c721c0c207', 'eada7dd6cde0eb1e', 'f57d4f7fee6ed178',
                '06f067aa72176fba', '0a637dc5a2c898a6', '113f9804bef90dae', '1b710b35131c471b',
                '28db77f523047d84', '32caab7b40c72493', '3c9ebe0a15c9bebc', '431d67c49c100d4c',
                '4cc5d4becb3e42b6', '597f299cfc657e2a', '5fcb6fab3ad6faec', '6c44198c4a475817'
            );

            for ($i = 0; $i < 80; $i++) {
                $k[$i] = new BigInteger($k[$i], 16);
            }
        }

        // Pre-processing
        $length = strlen($m);
        // to round to nearest 112 mod 128, we'll add 128 - (length + (128 - 112)) % 128
        $m.= str_repeat(chr(0), 128 - (($length + 16) & 0x7F));
        $m[$length] = chr(0x80);
        // we don't support hashing strings 512MB long
        $m.= pack('N4', 0, 0, 0, $length << 3);

        // Process the message in successive 1024-bit chunks
        $chunks = str_split($m, 128);
        foreach ($chunks as $chunk) {
            $w = array();
            for ($i = 0; $i < 16; $i++) {
                $temp = new BigInteger(self::_string_shift($chunk, 8), 256);
                $temp->setPrecision(64);
                $w[] = $temp;
            }

            // Extend the sixteen 32-bit words into eighty 32-bit words
            for ($i = 16; $i < 80; $i++) {
                $temp = array(
                          $w[$i - 15]->bitwise_rightRotate(1),
                          $w[$i - 15]->bitwise_rightRotate(8),
                          $w[$i - 15]->bitwise_rightShift(7)
                );
                $s0 = $temp[0]->bitwise_xor($temp[1]);
                $s0 = $s0->bitwise_xor($temp[2]);
                $temp = array(
                          $w[$i - 2]->bitwise_rightRotate(19),
                          $w[$i - 2]->bitwise_rightRotate(61),
                          $w[$i - 2]->bitwise_rightShift(6)
                );
                $s1 = $temp[0]->bitwise_xor($temp[1]);
                $s1 = $s1->bitwise_xor($temp[2]);
                $w[$i] = clone $w[$i - 16];
                $w[$i] = $w[$i]->add($s0);
                $w[$i] = $w[$i]->add($w[$i - 7]);
                $w[$i] = $w[$i]->add($s1);
            }

            // Initialize hash value for this chunk
            $a = clone $hash[0];
            $b = clone $hash[1];
            $c = clone $hash[2];
            $d = clone $hash[3];
            $e = clone $hash[4];
            $f = clone $hash[5];
            $g = clone $hash[6];
            $h = clone $hash[7];

            // Main loop
            for ($i = 0; $i < 80; $i++) {
                $temp = array(
                    $a->bitwise_rightRotate(28),
                    $a->bitwise_rightRotate(34),
                    $a->bitwise_rightRotate(39)
                );
                $s0 = $temp[0]->bitwise_xor($temp[1]);
                $s0 = $s0->bitwise_xor($temp[2]);
                $temp = array(
                    $a->bitwise_and($b),
                    $a->bitwise_and($c),
                    $b->bitwise_and($c)
                );
                $maj = $temp[0]->bitwise_xor($temp[1]);
                $maj = $maj->bitwise_xor($temp[2]);
                $t2 = $s0->add($maj);

                $temp = array(
                    $e->bitwise_rightRotate(14),
                    $e->bitwise_rightRotate(18),
                    $e->bitwise_rightRotate(41)
                );
                $s1 = $temp[0]->bitwise_xor($temp[1]);
                $s1 = $s1->bitwise_xor($temp[2]);
                $temp = array(
                    $e->bitwise_and($f),
                    $g->bitwise_and($e->bitwise_not())
                );
                $ch = $temp[0]->bitwise_xor($temp[1]);
                $t1 = $h->add($s1);
                $t1 = $t1->add($ch);
                $t1 = $t1->add($k[$i]);
                $t1 = $t1->add($w[$i]);

                $h = clone $g;
                $g = clone $f;
                $f = clone $e;
                $e = $d->add($t1);
                $d = clone $c;
                $c = clone $b;
                $b = clone $a;
                $a = $t1->add($t2);
            }

            // Add this chunk's hash to result so far
            $hash = array(
                $hash[0]->add($a),
                $hash[1]->add($b),
                $hash[2]->add($c),
                $hash[3]->add($d),
                $hash[4]->add($e),
                $hash[5]->add($f),
                $hash[6]->add($g),
                $hash[7]->add($h)
            );
        }

        // Produce the final hash value (big-endian)
        // (\phpseclib\Crypt\Hash::hash() trims the output for hashes but not for HMACs.  as such, we trim the output here)
        $temp = $hash[0]->toBytes() . $hash[1]->toBytes() . $hash[2]->toBytes() . $hash[3]->toBytes() .
                $hash[4]->toBytes() . $hash[5]->toBytes() . $hash[6]->toBytes() . $hash[7]->toBytes();

        return $temp;
    }

    /**
     * String Shift
     *
     * Inspired by array_shift
     *
     * @param string $string
     * @param int $index
     * @return string
     * @access private
     */
    static function _string_shift(&$string, $index = 1)
    {
        $substr = substr($string, 0, $index);
        $string = substr($string, $index);
        return $substr;
    }
}


code:
<?php

/**
 * Pure-PHP implementation of RC2.
 *
 * Uses mcrypt, if available, and an internal implementation, otherwise.
 *
 * PHP version 5
 *
 * Useful resources are as follows:
 *
 *  - {@link http://tools.ietf.org/html/rfc2268}
 *
 * Here's a short example of how to use this library:
 * <code>
 * <?php
 *    include 'vendor/autoload.php';
 *
 *    $rc2 = new \phpseclib\Crypt\RC2();
 *
 *    $rc2->setKey('abcdefgh');
 *
 *    $plaintext = str_repeat('a', 1024);
 *
 *    echo $rc2->decrypt($rc2->encrypt($plaintext));
 * ?>
 * </code>
 *
 * @category Crypt
 * @package  RC2
 * @author   Patrick Monnerat <pm@datasphere.ch>
 * @license  http://www.opensource.org/licenses/mit-license.html  MIT License
 * @link     http://phpseclib.sourceforge.net
 */

namespace phpseclib\Crypt;

/**
 * Pure-PHP implementation of RC2.
 *
 * @package RC2
 * @access  public
 */
class RC2 extends Base
{
    /**
     * Block Length of the cipher
     *
     * @see \phpseclib\Crypt\Base::block_size
     * @var int
     * @access private
     */
    var $block_size = 8;

    /**
     * The Key
     *
     * @see \phpseclib\Crypt\Base::key
     * @see self::setKey()
     * @var string
     * @access private
     */
    var $key;

    /**
     * The Original (unpadded) Key
     *
     * @see \phpseclib\Crypt\Base::key
     * @see self::setKey()
     * @see self::encrypt()
     * @see self::decrypt()
     * @var string
     * @access private
     */
    var $orig_key;

    /**
     * Don't truncate / null pad key
     *
     * @see \phpseclib\Crypt\Base::_clearBuffers()
     * @var bool
     * @access private
     */
    var $skip_key_adjustment = true;

    /**
     * Key Length (in bytes)
     *
     * @see \phpseclib\Crypt\RC2::setKeyLength()
     * @var int
     * @access private
     */
    var $key_length = 16; // = 128 bits

    /**
     * The mcrypt specific name of the cipher
     *
     * @see \phpseclib\Crypt\Base::cipher_name_mcrypt
     * @var string
     * @access private
     */
    var $cipher_name_mcrypt = 'rc2';

    /**
     * Optimizing value while CFB-encrypting
     *
     * @see \phpseclib\Crypt\Base::cfb_init_len
     * @var int
     * @access private
     */
    var $cfb_init_len = 500;

    /**
     * The key length in bits.
     *
     * @see self::setKeyLength()
     * @see self::setKey()
     * @var int
     * @access private
     * @internal Should be in range [1..1024].
     * @internal Changing this value after setting the key has no effect.
     */
    var $default_key_length = 1024;

    /**
     * The key length in bits.
     *
     * @see self::isValidEnine()
     * @see self::setKey()
     * @var int
     * @access private
     * @internal Should be in range [1..1024].
     */
    var $current_key_length;

    /**
     * The Key Schedule
     *
     * @see self::_setupKey()
     * @var array
     * @access private
     */
    var $keys;

    /**
     * Key expansion randomization table.
     * Twice the same 256-value sequence to save a modulus in key expansion.
     *
     * @see self::setKey()
     * @var array
     * @access private
     */
    var $pitable = array(
        0xD9, 0x78, 0xF9, 0xC4, 0x19, 0xDD, 0xB5, 0xED,
        0x28, 0xE9, 0xFD, 0x79, 0x4A, 0xA0, 0xD8, 0x9D,
        0xC6, 0x7E, 0x37, 0x83, 0x2B, 0x76, 0x53, 0x8E,
        0x62, 0x4C, 0x64, 0x88, 0x44, 0x8B, 0xFB, 0xA2,
        0x17, 0x9A, 0x59, 0xF5, 0x87, 0xB3, 0x4F, 0x13,
        0x61, 0x45, 0x6D, 0x8D, 0x09, 0x81, 0x7D, 0x32,
        0xBD, 0x8F, 0x40, 0xEB, 0x86, 0xB7, 0x7B, 0x0B,
        0xF0, 0x95, 0x21, 0x22, 0x5C, 0x6B, 0x4E, 0x82,
        0x54, 0xD6, 0x65, 0x93, 0xCE, 0x60, 0xB2, 0x1C,
        0x73, 0x56, 0xC0, 0x14, 0xA7, 0x8C, 0xF1, 0xDC,
        0x12, 0x75, 0xCA, 0x1F, 0x3B, 0xBE, 0xE4, 0xD1,
        0x42, 0x3D, 0xD4, 0x30, 0xA3, 0x3C, 0xB6, 0x26,
        0x6F, 0xBF, 0x0E, 0xDA, 0x46, 0x69, 0x07, 0x57,
        0x27, 0xF2, 0x1D, 0x9B, 0xBC, 0x94, 0x43, 0x03,
        0xF8, 0x11, 0xC7, 0xF6, 0x90, 0xEF, 0x3E, 0xE7,
        0x06, 0xC3, 0xD5, 0x2F, 0xC8, 0x66, 0x1E, 0xD7,
        0x08, 0xE8, 0xEA, 0xDE, 0x80, 0x52, 0xEE, 0xF7,
        0x84, 0xAA, 0x72, 0xAC, 0x35, 0x4D, 0x6A, 0x2A,
        0x96, 0x1A, 0xD2, 0x71, 0x5A, 0x15, 0x49, 0x74,
        0x4B, 0x9F, 0xD0, 0x5E, 0x04, 0x18, 0xA4, 0xEC,
        0xC2, 0xE0, 0x41, 0x6E, 0x0F, 0x51, 0xCB, 0xCC,
        0x24, 0x91, 0xAF, 0x50, 0xA1, 0xF4, 0x70, 0x39,
        0x99, 0x7C, 0x3A, 0x85, 0x23, 0xB8, 0xB4, 0x7A,
        0xFC, 0x02, 0x36, 0x5B, 0x25, 0x55, 0x97, 0x31,
        0x2D, 0x5D, 0xFA, 0x98, 0xE3, 0x8A, 0x92, 0xAE,
        0x05, 0xDF, 0x29, 0x10, 0x67, 0x6C, 0xBA, 0xC9,
        0xD3, 0x00, 0xE6, 0xCF, 0xE1, 0x9E, 0xA8, 0x2C,
        0x63, 0x16, 0x01, 0x3F, 0x58, 0xE2, 0x89, 0xA9,
        0x0D, 0x38, 0x34, 0x1B, 0xAB, 0x33, 0xFF, 0xB0,
        0xBB, 0x48, 0x0C, 0x5F, 0xB9, 0xB1, 0xCD, 0x2E,
        0xC5, 0xF3, 0xDB, 0x47, 0xE5, 0xA5, 0x9C, 0x77,
        0x0A, 0xA6, 0x20, 0x68, 0xFE, 0x7F, 0xC1, 0xAD,
        0xD9, 0x78, 0xF9, 0xC4, 0x19, 0xDD, 0xB5, 0xED,
        0x28, 0xE9, 0xFD, 0x79, 0x4A, 0xA0, 0xD8, 0x9D,
        0xC6, 0x7E, 0x37, 0x83, 0x2B, 0x76, 0x53, 0x8E,
        0x62, 0x4C, 0x64, 0x88, 0x44, 0x8B, 0xFB, 0xA2,
        0x17, 0x9A, 0x59, 0xF5, 0x87, 0xB3, 0x4F, 0x13,
        0x61, 0x45, 0x6D, 0x8D, 0x09, 0x81, 0x7D, 0x32,
        0xBD, 0x8F, 0x40, 0xEB, 0x86, 0xB7, 0x7B, 0x0B,
        0xF0, 0x95, 0x21, 0x22, 0x5C, 0x6B, 0x4E, 0x82,
        0x54, 0xD6, 0x65, 0x93, 0xCE, 0x60, 0xB2, 0x1C,
        0x73, 0x56, 0xC0, 0x14, 0xA7, 0x8C, 0xF1, 0xDC,
        0x12, 0x75, 0xCA, 0x1F, 0x3B, 0xBE, 0xE4, 0xD1,
        0x42, 0x3D, 0xD4, 0x30, 0xA3, 0x3C, 0xB6, 0x26,
        0x6F, 0xBF, 0x0E, 0xDA, 0x46, 0x69, 0x07, 0x57,
        0x27, 0xF2, 0x1D, 0x9B, 0xBC, 0x94, 0x43, 0x03,
        0xF8, 0x11, 0xC7, 0xF6, 0x90, 0xEF, 0x3E, 0xE7,
        0x06, 0xC3, 0xD5, 0x2F, 0xC8, 0x66, 0x1E, 0xD7,
        0x08, 0xE8, 0xEA, 0xDE, 0x80, 0x52, 0xEE, 0xF7,
        0x84, 0xAA, 0x72, 0xAC, 0x35, 0x4D, 0x6A, 0x2A,
        0x96, 0x1A, 0xD2, 0x71, 0x5A, 0x15, 0x49, 0x74,
        0x4B, 0x9F, 0xD0, 0x5E, 0x04, 0x18, 0xA4, 0xEC,
        0xC2, 0xE0, 0x41, 0x6E, 0x0F, 0x51, 0xCB, 0xCC,
        0x24, 0x91, 0xAF, 0x50, 0xA1, 0xF4, 0x70, 0x39,
        0x99, 0x7C, 0x3A, 0x85, 0x23, 0xB8, 0xB4, 0x7A,
        0xFC, 0x02, 0x36, 0x5B, 0x25, 0x55, 0x97, 0x31,
        0x2D, 0x5D, 0xFA, 0x98, 0xE3, 0x8A, 0x92, 0xAE,
        0x05, 0xDF, 0x29, 0x10, 0x67, 0x6C, 0xBA, 0xC9,
        0xD3, 0x00, 0xE6, 0xCF, 0xE1, 0x9E, 0xA8, 0x2C,
        0x63, 0x16, 0x01, 0x3F, 0x58, 0xE2, 0x89, 0xA9,
        0x0D, 0x38, 0x34, 0x1B, 0xAB, 0x33, 0xFF, 0xB0,
        0xBB, 0x48, 0x0C, 0x5F, 0xB9, 0xB1, 0xCD, 0x2E,
        0xC5, 0xF3, 0xDB, 0x47, 0xE5, 0xA5, 0x9C, 0x77,
        0x0A, 0xA6, 0x20, 0x68, 0xFE, 0x7F, 0xC1, 0xAD
    );

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

    /**
     * Default Constructor.
     *
     * @param int $mode
     * @access public
     * @throws \InvalidArgumentException if an invalid / unsupported mode is provided
     */
    function __construct($mode)
    {
        if ($mode == self::MODE_STREAM) {
            throw new \InvalidArgumentException('Block ciphers cannot be ran in stream mode');
        }

        parent::__construct($mode);
    }

    /**
     * Test for engine validity
     *
     * This is mainly just a wrapper to set things up for \phpseclib\Crypt\Base::isValidEngine()
     *
     * @see \phpseclib\Crypt\Base::__construct()
     * @param int $engine
     * @access public
     * @return bool
     */
    function isValidEngine($engine)
    {
        switch ($engine) {
            case self::ENGINE_OPENSSL:
                if ($this->current_key_length != 128 || strlen($this->orig_key) < 16) {
                    return false;
                }
                $this->cipher_name_openssl_ecb = 'rc2-ecb';
                $this->cipher_name_openssl = 'rc2-' . $this->_openssl_translate_mode();
        }

        return parent::isValidEngine($engine);
    }

    /**
     * Sets the key length.
     *
     * Valid key lengths are 8 to 1024.
     * Calling this function after setting the key has no effect until the next
     *  \phpseclib\Crypt\RC2::setKey() call.
     *
     * @access public
     * @param int $length in bits
     * @throws \LengthException if the key length isn't supported
     */
    function setKeyLength($length)
    {
        if ($length < 8 || $length > 1024) {
            throw new \LengthException('Key size of ' . $length . ' bits is not supported by this algorithm. Only keys between 1 and 1024 bits, inclusive, are supported');
        }

        $this->default_key_length = $this->current_key_length = $length;
    }

    /**
     * Returns the current key length
     *
     * @access public
     * @return int
     */
    function getKeyLength()
    {
        return $this->current_key_length;
    }

    /**
     * Sets the key.
     *
     * Keys can be of any length. RC2, itself, uses 8 to 1024 bit keys (eg.
     * strlen($key) <= 128), however, we only use the first 128 bytes if $key
     * has more then 128 bytes in it, and set $key to a single null byte if
     * it is empty.
     *
     * If the key is not explicitly set, it'll be assumed to be a single
     * null byte.
     *
     * @see \phpseclib\Crypt\Base::setKey()
     * @access public
     * @param string $key
     * @param int $t1 optional Effective key length in bits.
     * @throws \LengthException if the key length isn't supported
     */
    function setKey($key, $t1 = false)
    {
        $this->orig_key = $key;

        if ($t1 === false) {
            $t1 = $this->default_key_length;
        }

        if ($t1 < 1 || $t1 > 1024) {
            throw new \LengthException('Key size of ' . $length . ' bits is not supported by this algorithm. Only keys between 1 and 1024 bits, inclusive, are supported');
        }

        $this->current_key_length = $t1;
        // Key byte count should be 1..128.
        $key = strlen($key) ? substr($key, 0, 128) : "\x00";
        $t = strlen($key);

        // The mcrypt RC2 implementation only supports effective key length
        // of 1024 bits. It is however possible to handle effective key
        // lengths in range 1..1024 by expanding the key and applying
        // inverse pitable mapping to the first byte before submitting it
        // to mcrypt.

        // Key expansion.
        $l = array_values(unpack('C*', $key));
        $t8 = ($t1 + 7) >> 3;
        $tm = 0xFF >> (8 * $t8 - $t1);

        // Expand key.
        $pitable = $this->pitable;
        for ($i = $t; $i < 128; $i++) {
            $l[$i] = $pitable[$l[$i - 1] + $l[$i - $t]];
        }
        $i = 128 - $t8;
        $l[$i] = $pitable[$l[$i] & $tm];
        while ($i--) {
            $l[$i] = $pitable[$l[$i + 1] ^ $l[$i + $t8]];
        }

        // Prepare the key for mcrypt.
        $l[0] = $this->invpitable[$l[0]];
        array_unshift($l, 'C*');

        parent::setKey(call_user_func_array('pack', $l));
    }

    /**
     * Encrypts a message.
     *
     * Mostly a wrapper for \phpseclib\Crypt\Base::encrypt, with some additional OpenSSL handling code
     *
     * @see self::decrypt()
     * @access public
     * @param string $plaintext
     * @return string $ciphertext
     */
    function encrypt($plaintext)
    {
        if ($this->engine == self::ENGINE_OPENSSL) {
            $temp = $this->key;
            $this->key = $this->orig_key;
            $result = parent::encrypt($plaintext);
            $this->key = $temp;
            return $result;
        }

        return parent::encrypt($plaintext);
    }

    /**
     * Decrypts a message.
     *
     * Mostly a wrapper for \phpseclib\Crypt\Base::decrypt, with some additional OpenSSL handling code
     *
     * @see self::encrypt()
     * @access public
     * @param string $ciphertext
     * @return string $plaintext
     */
    function decrypt($ciphertext)
    {
        if ($this->engine == self::ENGINE_OPENSSL) {
            $temp = $this->key;
            $this->key = $this->orig_key;
            $result = parent::decrypt($ciphertext);
            $this->key = $temp;
            return $result;
        }

        return parent::decrypt($ciphertext);
    }

    /**
     * Encrypts a block
     *
     * @see \phpseclib\Crypt\Base::_encryptBlock()
     * @see \phpseclib\Crypt\Base::encrypt()
     * @access private
     * @param string $in
     * @return string
     */
    function _encryptBlock($in)
    {
        list($r0, $r1, $r2, $r3) = array_values(unpack('v*', $in));
        $keys = $this->keys;
        $limit = 20;
        $actions = array($limit => 44, 44 => 64);
        $j = 0;

        for (;;) {
            // Mixing round.
            $r0 = (($r0 + $keys[$j++] + ((($r1 ^ $r2) & $r3) ^ $r1)) & 0xFFFF) << 1;
            $r0 |= $r0 >> 16;
            $r1 = (($r1 + $keys[$j++] + ((($r2 ^ $r3) & $r0) ^ $r2)) & 0xFFFF) << 2;
            $r1 |= $r1 >> 16;
            $r2 = (($r2 + $keys[$j++] + ((($r3 ^ $r0) & $r1) ^ $r3)) & 0xFFFF) << 3;
            $r2 |= $r2 >> 16;
            $r3 = (($r3 + $keys[$j++] + ((($r0 ^ $r1) & $r2) ^ $r0)) & 0xFFFF) << 5;
            $r3 |= $r3 >> 16;

            if ($j === $limit) {
                if ($limit === 64) {
                    break;
                }

                // Mashing round.
                $r0 += $keys[$r3 & 0x3F];
                $r1 += $keys[$r0 & 0x3F];
                $r2 += $keys[$r1 & 0x3F];
                $r3 += $keys[$r2 & 0x3F];
                $limit = $actions[$limit];
            }
        }

        return pack('vvvv', $r0, $r1, $r2, $r3);
    }

    /**
     * Decrypts a block
     *
     * @see \phpseclib\Crypt\Base::_decryptBlock()
     * @see \phpseclib\Crypt\Base::decrypt()
     * @access private
     * @param string $in
     * @return string
     */
    function _decryptBlock($in)
    {
        list($r0, $r1, $r2, $r3) = array_values(unpack('v*', $in));
        $keys = $this->keys;
        $limit = 44;
        $actions = array($limit => 20, 20 => 0);
        $j = 64;

        for (;;) {
            // R-mixing round.
            $r3 = ($r3 | ($r3 << 16)) >> 5;
            $r3 = ($r3 - $keys[--$j] - ((($r0 ^ $r1) & $r2) ^ $r0)) & 0xFFFF;
            $r2 = ($r2 | ($r2 << 16)) >> 3;
            $r2 = ($r2 - $keys[--$j] - ((($r3 ^ $r0) & $r1) ^ $r3)) & 0xFFFF;
            $r1 = ($r1 | ($r1 << 16)) >> 2;
            $r1 = ($r1 - $keys[--$j] - ((($r2 ^ $r3) & $r0) ^ $r2)) & 0xFFFF;
            $r0 = ($r0 | ($r0 << 16)) >> 1;
            $r0 = ($r0 - $keys[--$j] - ((($r1 ^ $r2) & $r3) ^ $r1)) & 0xFFFF;

            if ($j === $limit) {
                if ($limit === 0) {
                    break;
                }

                // R-mashing round.
                $r3 = ($r3 - $keys[$r2 & 0x3F]) & 0xFFFF;
                $r2 = ($r2 - $keys[$r1 & 0x3F]) & 0xFFFF;
                $r1 = ($r1 - $keys[$r0 & 0x3F]) & 0xFFFF;
                $r0 = ($r0 - $keys[$r3 & 0x3F]) & 0xFFFF;
                $limit = $actions[$limit];
            }
        }

        return pack('vvvv', $r0, $r1, $r2, $r3);
    }

    /**
     * Setup the \phpseclib\Crypt\Base::ENGINE_MCRYPT $engine
     *
     * @see \phpseclib\Crypt\Base::_setupMcrypt()
     * @access private
     */
    function _setupMcrypt()
    {
        if (!isset($this->key)) {
            $this->setKey('');
        }

        parent::_setupMcrypt();
    }

    /**
     * Creates the key schedule
     *
     * @see \phpseclib\Crypt\Base::_setupKey()
     * @access private
     */
    function _setupKey()
    {
        if (!isset($this->key)) {
            $this->setKey('');
        }

        // Key has already been expanded in \phpseclib\Crypt\RC2::setKey():
        // Only the first value must be altered.
        $l = unpack('Ca/Cb/v*', $this->key);
        array_unshift($l, $this->pitable[$l['a']] | ($l['b'] << 8));
        unset($l['a']);
        unset($l['b']);
        $this->keys = $l;
    }

    /**
     * Setup the performance-optimized function for de/encrypt()
     *
     * @see \phpseclib\Crypt\Base::_setupInlineCrypt()
     * @access private
     */
    function _setupInlineCrypt()
    {
        $lambda_functions =& self::_getLambdaFunctions();

        // The first 10 generated $lambda_functions will use the $keys hardcoded as integers
        // for the mixing rounds, for better inline crypt performance [~20% faster].
        // But for memory reason we have to limit those ultra-optimized $lambda_functions to an amount of 10.
        // (Currently, for Crypt_RC2, one generated $lambda_function cost on php5.5@32bit ~60kb unfreeable mem and ~100kb on php5.5@64bit)
        $gen_hi_opt_code = (bool)(count($lambda_functions) < 10);

        // Generation of a uniqe hash for our generated code
        $code_hash = "Crypt_RC2, {$this->mode}";
        if ($gen_hi_opt_code) {
            $code_hash = str_pad($code_hash, 32) . $this->_hashInlineCryptFunction($this->key);
        }

        // Is there a re-usable $lambda_functions in there?
        // If not, we have to create it.
        if (!isset($lambda_functions[$code_hash])) {
            // Init code for both, encrypt and decrypt.
            $init_crypt = '$keys = $self->keys;';

            switch (true) {
                case $gen_hi_opt_code:
                    $keys = $this->keys;
                default:
                    $keys = array();
                    foreach ($this->keys as $k => $v) {
                        $keys[$k] = '$keys[' . $k . ']';
                    }
            }

            // $in is the current 8 bytes block which has to be en/decrypt
            $encrypt_block = $decrypt_block = '
                $in = unpack("v4", $in);
                $r0 = $in[1];
                $r1 = $in[2];
                $r2 = $in[3];
                $r3 = $in[4];
            ';

            // Create code for encryption.
            $limit = 20;
            $actions = array($limit => 44, 44 => 64);
            $j = 0;

            for (;;) {
                // Mixing round.
                $encrypt_block .= '
                    $r0 = (($r0 + ' . $keys[$j++] . ' +
                           ((($r1 ^ $r2) & $r3) ^ $r1)) & 0xFFFF) << 1;
                    $r0 |= $r0 >> 16;
                    $r1 = (($r1 + ' . $keys[$j++] . ' +
                           ((($r2 ^ $r3) & $r0) ^ $r2)) & 0xFFFF) << 2;
                    $r1 |= $r1 >> 16;
                    $r2 = (($r2 + ' . $keys[$j++] . ' +
                           ((($r3 ^ $r0) & $r1) ^ $r3)) & 0xFFFF) << 3;
                    $r2 |= $r2 >> 16;
                    $r3 = (($r3 + ' . $keys[$j++] . ' +
                           ((($r0 ^ $r1) & $r2) ^ $r0)) & 0xFFFF) << 5;
                    $r3 |= $r3 >> 16;';

                if ($j === $limit) {
                    if ($limit === 64) {
                        break;
                    }

                    // Mashing round.
                    $encrypt_block .= '
                        $r0 += $keys[$r3 & 0x3F];
                        $r1 += $keys[$r0 & 0x3F];
                        $r2 += $keys[$r1 & 0x3F];
                        $r3 += $keys[$r2 & 0x3F];';
                    $limit = $actions[$limit];
                }
            }

            $encrypt_block .= '$in = pack("v4", $r0, $r1, $r2, $r3);';

            // Create code for decryption.
            $limit = 44;
            $actions = array($limit => 20, 20 => 0);
            $j = 64;

            for (;;) {
                // R-mixing round.
                $decrypt_block .= '
                    $r3 = ($r3 | ($r3 << 16)) >> 5;
                    $r3 = ($r3 - ' . $keys[--$j] . ' -
                           ((($r0 ^ $r1) & $r2) ^ $r0)) & 0xFFFF;
                    $r2 = ($r2 | ($r2 << 16)) >> 3;
                    $r2 = ($r2 - ' . $keys[--$j] . ' -
                           ((($r3 ^ $r0) & $r1) ^ $r3)) & 0xFFFF;
                    $r1 = ($r1 | ($r1 << 16)) >> 2;
                    $r1 = ($r1 - ' . $keys[--$j] . ' -
                           ((($r2 ^ $r3) & $r0) ^ $r2)) & 0xFFFF;
                    $r0 = ($r0 | ($r0 << 16)) >> 1;
                    $r0 = ($r0 - ' . $keys[--$j] . ' -
                           ((($r1 ^ $r2) & $r3) ^ $r1)) & 0xFFFF;';

                if ($j === $limit) {
                    if ($limit === 0) {
                        break;
                    }

                    // R-mashing round.
                    $decrypt_block .= '
                        $r3 = ($r3 - $keys[$r2 & 0x3F]) & 0xFFFF;
                        $r2 = ($r2 - $keys[$r1 & 0x3F]) & 0xFFFF;
                        $r1 = ($r1 - $keys[$r0 & 0x3F]) & 0xFFFF;
                        $r0 = ($r0 - $keys[$r3 & 0x3F]) & 0xFFFF;';
                    $limit = $actions[$limit];
                }
            }

            $decrypt_block .= '$in = pack("v4", $r0, $r1, $r2, $r3);';

            // Creates the inline-crypt function
            $lambda_functions[$code_hash] = $this->_createInlineCryptFunction(
                array(
                   'init_crypt'    => $init_crypt,
                   'encrypt_block' => $encrypt_block,
                   'decrypt_block' => $decrypt_block
                )
            );
        }

        // Set the inline-crypt function as callback in: $this->inline_crypt
        $this->inline_crypt = $lambda_functions[$code_hash];
    }
}

repo_name: ksuudilla/gnu

license: mit


code:
<?php

/**
 * Pure-PHP implementation of RC4.
 *
 * Uses mcrypt, if available, and an internal implementation, otherwise.
 *
 * PHP version 5
 *
 * Useful resources are as follows:
 *
 *  - {@link http://www.mozilla.org/projects/security/pki/nss/draft-kaukonen-cipher-arcfour-03.txt ARCFOUR Algorithm}
 *  - {@link http://en.wikipedia.org/wiki/RC4 - Wikipedia: RC4}
 *
 * RC4 is also known as ARCFOUR or ARC4.  The reason is elaborated upon at Wikipedia.  This class is named RC4 and not
 * ARCFOUR or ARC4 because RC4 is how it is referred to in the SSH1 specification.
 *
 * Here's a short example of how to use this library:
 * <code>
 * <?php
 *    include 'vendor/autoload.php';
 *
 *    $rc4 = new \phpseclib\Crypt\RC4();
 *
 *    $rc4->setKey('abcdefgh');
 *
 *    $size = 10 * 1024;
 *    $plaintext = '';
 *    for ($i = 0; $i < $size; $i++) {
 *        $plaintext.= 'a';
 *    }
 *
 *    echo $rc4->decrypt($rc4->encrypt($plaintext));
 * ?>
 * </code>
 *
 * @category  Crypt
 * @package   RC4
 * @author    Jim Wigginton <terrafrost@php.net>
 * @copyright 2007 Jim Wigginton
 * @license   http://www.opensource.org/licenses/mit-license.html  MIT License
 * @link      http://phpseclib.sourceforge.net
 */

namespace phpseclib\Crypt;

/**
 * Pure-PHP implementation of RC4.
 *
 * @package RC4
 * @author  Jim Wigginton <terrafrost@php.net>
 * @access  public
 */
class RC4 extends Base
{
    /**#@+
     * @access private
     * @see \phpseclib\Crypt\RC4::_crypt()
    */
    const ENCRYPT = 0;
    const DECRYPT = 1;
    /**#@-*/

    /**
     * Block Length of the cipher
     *
     * RC4 is a stream cipher
     * so we the block_size to 0
     *
     * @see \phpseclib\Crypt\Base::block_size
     * @var int
     * @access private
     */
    var $block_size = 0;

    /**
     * Key Length (in bytes)
     *
     * @see \phpseclib\Crypt\RC4::setKeyLength()
     * @var int
     * @access private
     */
    var $key_length = 128; // = 1024 bits

    /**
     * The mcrypt specific name of the cipher
     *
     * @see \phpseclib\Crypt\Base::cipher_name_mcrypt
     * @var string
     * @access private
     */
    var $cipher_name_mcrypt = 'arcfour';

    /**
     * Holds whether performance-optimized $inline_crypt() can/should be used.
     *
     * @see \phpseclib\Crypt\Base::inline_crypt
     * @var mixed
     * @access private
     */
    var $use_inline_crypt = false; // currently not available

    /**
     * The Key
     *
     * @see self::setKey()
     * @var string
     * @access private
     */
    var $key = "\0";

    /**
     * The Key Stream for decryption and encryption
     *
     * @see self::setKey()
     * @var array
     * @access private
     */
    var $stream;

    /**
     * Default Constructor.
     *
     * @see \phpseclib\Crypt\Base::__construct()
     * @return \phpseclib\Crypt\RC4
     * @access public
     */
    function __construct()
    {
        parent::__construct(Base::MODE_STREAM);
    }

    /**
     * Test for engine validity
     *
     * This is mainly just a wrapper to set things up for \phpseclib\Crypt\Base::isValidEngine()
     *
     * @see \phpseclib\Crypt\Base::__construct()
     * @param int $engine
     * @access public
     * @return bool
     */
    function isValidEngine($engine)
    {
        switch ($engine) {
            case Base::ENGINE_OPENSSL:
                switch (strlen($this->key)) {
                    case 5:
                        $this->cipher_name_openssl = 'rc4-40';
                        break;
                    case 8:
                        $this->cipher_name_openssl = 'rc4-64';
                        break;
                    case 16:
                        $this->cipher_name_openssl = 'rc4';
                        break;
                    default:
                        return false;
                }
        }

        return parent::isValidEngine($engine);
    }

    /**
     * RC4 does not use an IV
     *
     * @access public
     * @return bool
     */
    function usesIV()
    {
        return false;
    }

    /**
     * Sets the key length
     *
     * Keys can be between 1 and 256 bytes long.
     *
     * @access public
     * @param int $length
     * @throws \LengthException if the key length is invalid
     */
    function setKeyLength($length)
    {
        if ($length < 8 || $length > 2048) {
            throw new \LengthException('Key size of ' . $length . ' bits is not supported by this algorithm. Only keys between 1 and 256 bytes are supported');
        }

        $this->key_length = $length >> 3;

        parent::setKeyLength($length);
    }

    /**
     * Sets the key length
     *
     * Keys can be between 1 and 256 bytes long.
     *
     * @access public
     * @param int $length
     * @throws \LengthException if the key length is invalid
     */
    function setKey($key)
    {
        $length = strlen($key);
        if ($length < 1 || $length > 256) {
            throw new \LengthException('Key size of ' . $length . ' bytes is not supported by RC4. Keys must be between 1 and 256 bytes long');
        }

        parent::setKey($key);
    }

    /**
     * Encrypts a message.
     *
     * @see \phpseclib\Crypt\Base::decrypt()
     * @see self::_crypt()
     * @access public
     * @param string $plaintext
     * @return string $ciphertext
     */
    function encrypt($plaintext)
    {
        if ($this->engine != Base::ENGINE_INTERNAL) {
            return parent::encrypt($plaintext);
        }
        return $this->_crypt($plaintext, self::ENCRYPT);
    }

    /**
     * Decrypts a message.
     *
     * $this->decrypt($this->encrypt($plaintext)) == $this->encrypt($this->encrypt($plaintext)).
     * At least if the continuous buffer is disabled.
     *
     * @see \phpseclib\Crypt\Base::encrypt()
     * @see self::_crypt()
     * @access public
     * @param string $ciphertext
     * @return string $plaintext
     */
    function decrypt($ciphertext)
    {
        if ($this->engine != Base::ENGINE_INTERNAL) {
            return parent::decrypt($ciphertext);
        }
        return $this->_crypt($ciphertext, self::DECRYPT);
    }

    /**
     * Encrypts a block
     *
     * @access private
     * @param string $in
     */
    function _encryptBlock($in)
    {
        // RC4 does not utilize this method
    }

    /**
     * Decrypts a block
     *
     * @access private
     * @param string $in
     */
    function _decryptBlock($in)
    {
        // RC4 does not utilize this method
    }

    /**
     * Setup the key (expansion)
     *
     * @see \phpseclib\Crypt\Base::_setupKey()
     * @access private
     */
    function _setupKey()
    {
        $key = $this->key;
        $keyLength = strlen($key);
        $keyStream = range(0, 255);
        $j = 0;
        for ($i = 0; $i < 256; $i++) {
            $j = ($j + $keyStream[$i] + ord($key[$i % $keyLength])) & 255;
            $temp = $keyStream[$i];
            $keyStream[$i] = $keyStream[$j];
            $keyStream[$j] = $temp;
        }

        $this->stream = array();
        $this->stream[self::DECRYPT] = $this->stream[self::ENCRYPT] = array(
            0, // index $i
            0, // index $j
            $keyStream
        );
    }

    /**
     * Encrypts or decrypts a message.
     *
     * @see self::encrypt()
     * @see self::decrypt()
     * @access private
     * @param string $text
     * @param int $mode
     * @return string $text
     */
    function _crypt($text, $mode)
    {
        if ($this->changed) {
            $this->_setup();
            $this->changed = false;
        }

        $stream = &$this->stream[$mode];
        if ($this->continuousBuffer) {
            $i = &$stream[0];
            $j = &$stream[1];
            $keyStream = &$stream[2];
        } else {
            $i = $stream[0];
            $j = $stream[1];
            $keyStream = $stream[2];
        }

        $len = strlen($text);
        for ($k = 0; $k < $len; ++$k) {
            $i = ($i + 1) & 255;
            $ksi = $keyStream[$i];
            $j = ($j + $ksi) & 255;
            $ksj = $keyStream[$j];

            $keyStream[$i] = $ksj;
            $keyStream[$j] = $ksi;
            $text[$k] = $text[$k] ^ chr($keyStream[($ksj + $ksi) & 255]);
        }

        return $text;
    }
}