* setKey('abcdefgh'); * * $size = 10 * 1024; * $plaintext = ''; * for ($i = 0; $i < $size; $i++) { * $plaintext.= 'a'; * } * * echo $rc4->decrypt($rc4->encrypt($plaintext)); * ?> * * * @category Crypt * @package RC4 * @author Jim Wigginton * @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 * @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. * * Determines whether or not the mcrypt extension should be used. * * @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); } /** * Dummy function. * * Some protocols, such as WEP, prepend an "initialization vector" to the key, effectively creating a new key [1]. * If you need to use an initialization vector in this manner, feel free to prepend it to the key, yourself, before * calling setKey(). * * [1] WEP's initialization vectors (IV's) are used in a somewhat insecure way. Since, in that protocol, * the IV's are relatively easy to predict, an attack described by * {@link http://www.drizzle.com/~aboba/IEEE/rc4_ksaproc.pdf Scott Fluhrer, Itsik Mantin, and Adi Shamir} * can be used to quickly guess at the rest of the key. The following links elaborate: * * {@link http://www.rsa.com/rsalabs/node.asp?id=2009 http://www.rsa.com/rsalabs/node.asp?id=2009} * {@link http://en.wikipedia.org/wiki/Related_key_attack http://en.wikipedia.org/wiki/Related_key_attack} * * @param string $iv * @see self::setKey() * @access public */ function setIV($iv) { } /** * Sets the key length * * Keys can be between 1 and 256 bytes long. * * @access public * @param int $length */ function setKeyLength($length) { if ($length < 8) { $this->key_length = 1; } elseif ($length > 2048) { $this->key_length = 256; } else { $this->key_length = $length >> 3; } parent::setKeyLength($length); } /** * 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; } }