Subversion Repositories oidplus

<?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 \phpseclib3\Crypt\RC2('ctr');

 *

 *    $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 phpseclib3\Crypt;

use phpseclib3\Crypt\Common\BlockCipher;

use phpseclib3\Exception\BadModeException;

/**

 * Pure-PHP implementation of RC2.

 *

 * @package RC2

 * @access  public

 */

class RC2 extends BlockCipher

{

    /**

     * Block Length of the cipher

     *

     * @see \phpseclib3\Crypt\Common\SymmetricKey::block_size

     * @var int

     * @access private

     */

    protected $block_size = 8;

    /**

     * The Key

     *

     * @see \phpseclib3\Crypt\Common\SymmetricKey::key

     * @see self::setKey()

     * @var string

     * @access private

     */

    protected $key;

    /**

     * The Original (unpadded) Key

     *

     * @see \phpseclib3\Crypt\Common\SymmetricKey::key

     * @see self::setKey()

     * @see self::encrypt()

     * @see self::decrypt()

     * @var string

     * @access private

     */

    private $orig_key;

    /**

     * Don't truncate / null pad key

     *

     * @see \phpseclib3\Crypt\Common\SymmetricKey::clearBuffers()

     * @var bool

     * @access private

     */

    private $skip_key_adjustment = true;

    /**

     * Key Length (in bytes)

     *

     * @see \phpseclib3\Crypt\RC2::setKeyLength()

     * @var int

     * @access private

     */

    protected $key_length = 16; // = 128 bits

    /**

     * The mcrypt specific name of the cipher

     *

     * @see \phpseclib3\Crypt\Common\SymmetricKey::cipher_name_mcrypt

     * @var string

     * @access private

     */

    protected $cipher_name_mcrypt = 'rc2';

    /**

     * Optimizing value while CFB-encrypting

     *

     * @see \phpseclib3\Crypt\Common\SymmetricKey::cfb_init_len

     * @var int

     * @access private

     */

    protected $cfb_init_len = 500;

    /**

     * The key length in bits.

     *

     * {@internal Should be in range [1..1024].}

     *

     * {@internal Changing this value after setting the key has no effect.}

     *

     * @see self::setKeyLength()

     * @see self::setKey()

     * @var int

     * @access private

     */

    private $default_key_length = 1024;

    /**

     * The key length in bits.

     *

     * {@internal Should be in range [1..1024].}

     *

     * @see self::isValidEnine()

     * @see self::setKey()

     * @var int

     * @access private

     */

    private $current_key_length;

    /**

     * The Key Schedule

     *

     * @see self::setupKey()

     * @var array

     * @access private

     */

    private $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

     */

    private static $pitable = [

        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

     */

    private static $invpitable = [

        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 string $mode

     * @access public

     * @throws \InvalidArgumentException if an invalid / unsupported mode is provided

     */

    public function __construct($mode)

    {

        parent::__construct($mode);

        if ($this->mode == self::MODE_STREAM) {

            throw new BadModeException('Block ciphers cannot be ran in stream mode');

        }

    }

    /**

     * Test for engine validity

     *

     * This is mainly just a wrapper to set things up for \phpseclib3\Crypt\Common\SymmetricKey::isValidEngine()

     *

     * @see \phpseclib3\Crypt\Common\SymmetricKey::__construct()

     * @param int $engine

     * @access protected

     * @return bool

     */

    protected function isValidEngineHelper($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::isValidEngineHelper($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

     *  \phpseclib3\Crypt\RC2::setKey() call.

     *

     * @access public

     * @param int $length in bits

     * @throws \LengthException if the key length isn't supported

     */

    public 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;

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

    }

    /**

     * Returns the current key length

     *

     * @access public

     * @return int

     */

    public 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.

     *

     * @see \phpseclib3\Crypt\Common\SymmetricKey::setKey()

     * @access public

     * @param string $key

     * @param int|boolean $t1 optional Effective key length in bits.

     * @throws \LengthException if the key length isn't supported

     */

    public 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;

        if (strlen($key) < 1 || strlen($key) > 128) {

            throw new \LengthException('Key of size ' . strlen($key) . ' not supported by this algorithm. Only keys of sizes between 8 and 1024 bits, inclusive, are supported');

        }

        $t = strlen($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.

        $pitable = self::$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.

        $l[0] = self::$invpitable[$l[0]];

        array_unshift($l, 'C*');

        $this->key = pack(...$l);

        $this->key_length = strlen($this->key);

        $this->changed = $this->nonIVChanged = true;

        $this->setEngine();

    }

    /**

     * Encrypts a message.

     *

     * Mostly a wrapper for \phpseclib3\Crypt\Common\SymmetricKey::encrypt, with some additional OpenSSL handling code

     *

     * @see self::decrypt()

     * @access public

     * @param string $plaintext

     * @return string $ciphertext

     */

    public 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 \phpseclib3\Crypt\Common\SymmetricKey::decrypt, with some additional OpenSSL handling code

     *

     * @see self::encrypt()

     * @access public

     * @param string $ciphertext

     * @return string $plaintext

     */

    public 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 \phpseclib3\Crypt\Common\SymmetricKey::encryptBlock()

     * @see \phpseclib3\Crypt\Common\SymmetricKey::encrypt()

     * @access private

     * @param string $in

     * @return string

     */

    protected function encryptBlock($in)

    {

        list($r0, $r1, $r2, $r3) = array_values(unpack('v*', $in));

        $keys = $this->keys;

        $limit = 20;

        $actions = [$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 \phpseclib3\Crypt\Common\SymmetricKey::decryptBlock()

     * @see \phpseclib3\Crypt\Common\SymmetricKey::decrypt()

     * @access private

     * @param string $in

     * @return string

     */

    protected function decryptBlock($in)

    {

        list($r0, $r1, $r2, $r3) = array_values(unpack('v*', $in));

        $keys = $this->keys;

        $limit = 44;

        $actions = [$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);

    }

    /**

     * Creates the key schedule

     *

     * @see \phpseclib3\Crypt\Common\SymmetricKey::setupKey()

     * @access private

     */

    protected function setupKey()

    {

        if (!isset($this->key)) {

            $this->setKey('');

        }

        // Key has already been expanded in \phpseclib3\Crypt\RC2::setKey():

        // Only the first value must be altered.

        $l = unpack('Ca/Cb/v*', $this->key);

        array_unshift($l, self::$pitable[$l['a']] | ($l['b'] << 8));

        unset($l['a']);

        unset($l['b']);

        $this->keys = $l;

    }

    /**

     * Setup the performance-optimized function for de/encrypt()

     *

     * @see \phpseclib3\Crypt\Common\SymmetricKey::setupInlineCrypt()

     * @access private

     */

    protected function setupInlineCrypt()

    {

        // Init code for both, encrypt and decrypt.

        $init_crypt = '$keys = $this->keys;';

        $keys = $this->keys;

        // $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;

        $actions = [$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;

        $actions = [$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] . ' -