* 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; use phpseclib\Crypt\Common\StreamCipher; /** * Pure-PHP implementation of RC4. * * @package RC4 * @author Jim Wigginton * @access public */ class RC4 extends StreamCipher { /**#@+ * @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\Common\SymmetricKey::block_size * @var int * @access private */ protected $block_size = 0; /** * Key Length (in bytes) * * @see \phpseclib\Crypt\RC4::setKeyLength() * @var int * @access private */ protected $key_length = 128; // = 1024 bits /** * The mcrypt specific name of the cipher * * @see \phpseclib\Crypt\Common\SymmetricKey::cipher_name_mcrypt * @var string * @access private */ protected $cipher_name_mcrypt = 'arcfour'; /** * Holds whether performance-optimized $inline_crypt() can/should be used. * * @see \phpseclib\Crypt\Common\SymmetricKey::inline_crypt * @var mixed * @access private */ protected $use_inline_crypt = false; // currently not available /** * The Key * * @see self::setKey() * @var string * @access private */ protected $key; /** * The Key Stream for decryption and encryption * * @see self::setKey() * @var array * @access private */ private $stream; /** * Default Constructor. * * @see \phpseclib\Crypt\Common\SymmetricKey::__construct() * @return \phpseclib\Crypt\RC4 * @access public */ public function __construct() { parent::__construct('stream'); } /** * Test for engine validity * * This is mainly just a wrapper to set things up for \phpseclib\Crypt\Common\SymmetricKey::isValidEngine() * * @see \phpseclib\Crypt\Common\SymmetricKey::__construct() * @param int $engine * @access protected * @return bool */ protected function isValidEngineHelper($engine) { if ($engine == self::ENGINE_OPENSSL) { if (version_compare(PHP_VERSION, '5.3.7') >= 0) { $this->cipher_name_openssl = 'rc4-40'; } else { switch (strlen($this->key)) { case 5: $this->cipher_name_openssl = 'rc4-40'; break; case 8: $this->cipher_name_openssl = 'rc4-64'; break; case 16: $this->cipher_name_openssl = 'rc4'; break; default: return false; } } } return parent::isValidEngineHelper($engine); } /** * RC4 does not use an IV * * @access public * @return bool */ public function usesIV() { return false; } /** * Sets the key length * * Keys can be between 1 and 256 bytes long. * * @access public * @param int $length * @throws \LengthException if the key length is invalid */ public function setKeyLength($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 $length * @throws \LengthException if the key length is invalid */ public function setKey($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\Common\SymmetricKey::decrypt() * @see self::crypt() * @access public * @param string $plaintext * @return string $ciphertext */ public function encrypt($plaintext) { if ($this->engine != self::ENGINE_INTERNAL) { return parent::encrypt($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\Common\SymmetricKey::encrypt() * @see self::crypt() * @access public * @param string $ciphertext * @return string $plaintext */ public function decrypt($ciphertext) { if ($this->engine != self::ENGINE_INTERNAL) { return parent::decrypt($ciphertext); } return $this->crypt($ciphertext, self::DECRYPT); } /** * Encrypts a block * * @access private * @param string $in */ protected function encryptBlock($in) { // RC4 does not utilize this method } /** * Decrypts a block * * @access private * @param string $in */ protected function decryptBlock($in) { // RC4 does not utilize this method } /** * Setup the key (expansion) * * @see \phpseclib\Crypt\Common\SymmetricKey::_setupKey() * @access private */ protected 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 = []; $this->stream[self::DECRYPT] = $this->stream[self::ENCRYPT] = [ 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 $text */ private function crypt($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; } }