RC4.php

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<?php
 
namespace phpseclib\Crypt;
 
use phpseclib\Crypt\Base;
 
class RC4 extends Base
{
    const ENCRYPT = 0;
    const DECRYPT = 1;
    var $block_size = 0;
 
    var $key_length = 128; // = 1024 bits
 
    var $cipher_name_mcrypt = 'arcfour';
 
    var $use_inline_crypt = false; // currently not available
 
    var $key = "\0";
 
    var $stream;
 
    function __construct()
    {
        parent::__construct(Base::MODE_STREAM);
    }
 
    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);
    }
 
    function setIV($iv)
    {
    }
 
    function setKeyLength($length)
    {
        if ($length < 8) {
            $this->key_length = 1;
        } elseif ($length > 2048) {
            $this->key_length = 248;
        } else {
            $this->key_length = $length >> 3;
        }
 
        parent::setKeyLength($length);
    }
 
    function encrypt($plaintext)
    {
        if ($this->engine != Base::ENGINE_INTERNAL) {
            return parent::encrypt($plaintext);
        }
        return $this->_crypt($plaintext, self::ENCRYPT);
    }
 
    function decrypt($ciphertext)
    {
        if ($this->engine != Base::ENGINE_INTERNAL) {
            return parent::decrypt($ciphertext);
        }
        return $this->_crypt($ciphertext, self::DECRYPT);
    }
 
    function _encryptBlock($in)
    {
        // RC4 does not utilize this method
    }
 
    function _decryptBlock($in)
    {
        // RC4 does not utilize this method
    }
 
    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
        );
    }
 
    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;
    }
}