php实现的rc4加密解密类定义与用法示例

<?php
/* 
 * by julying.com
 */
define('crypt_rc4_mode_internal', 1);
define('crypt_rc4_mode_mcrypt', 2);
define('crypt_rc4_encrypt', 0);
define('crypt_rc4_decrypt', 1);
class crypt_rc4 {
 /**
  * the key
  *
  * @see crypt_rc4::setkey()
  * @var string
  * @access private
  */
 var $key = "\0";
 /**
  * the key stream for encryption
  *
  * if crypt_rc4_mode == crypt_rc4_mode_mcrypt, this will be equal to the mcrypt object
  *
  * @see crypt_rc4::setkey()
  * @var array
  * @access private
  */
 var $encryptstream = false;
 /**
  * the key stream for decryption
  *
  * if crypt_rc4_mode == crypt_rc4_mode_mcrypt, this will be equal to the mcrypt object
  *
  * @see crypt_rc4::setkey()
  * @var array
  * @access private
  */
 var $decryptstream = false;
 /**
  * the $i and $j indexes for encryption
  *
  * @see crypt_rc4::_crypt()
  * @var integer
  * @access private
  */
 var $encryptindex = 0;
 /**
  * the $i and $j indexes for decryption
  *
  * @see crypt_rc4::_crypt()
  * @var integer
  * @access private
  */
 var $decryptindex = 0;
 /**
  * mcrypt parameters
  *
  * @see crypt_rc4::setmcrypt()
  * @var array
  * @access private
  */
 var $mcrypt = array('', '');
 /**
  * the encryption algorithm
  *
  * only used if crypt_rc4_mode == crypt_rc4_mode_mcrypt. only possible values are mcrypt_rc4 or mcrypt_arcfour.
  *
  * @see crypt_rc4::crypt_rc4()
  * @var integer
  * @access private
  */
 var $mode;
 /**
  * default constructor.
  *
  * determines whether or not the mcrypt extension should be used.
  *
  * @param optional integer $mode
  * @return crypt_rc4
  * @access public
  */
 var $continuousbuffer ;
 function crypt_rc4()
 {
  if ( !defined('crypt_rc4_mode') ) {
   switch (true) {
    case extension_loaded('mcrypt') && (defined('mcrypt_arcfour') || defined('mcrypt_rc4')):
     // i'd check to see if rc4 was supported, by doing in_array('arcfour', mcrypt_list_algorithms('')),
     // but since that can be changed after the object has been created, there doesn't seem to be
     // a lot of point...
     define('crypt_rc4_mode', crypt_rc4_mode_mcrypt);
     break;
    default:
     define('crypt_rc4_mode', crypt_rc4_mode_internal);
   }
  }
  switch ( crypt_rc4_mode ) {
   case crypt_rc4_mode_mcrypt:
    switch (true) {
     case defined('mcrypt_arcfour'):
      $this->mode = mcrypt_arcfour;
      break;
     case defined('mcrypt_rc4');
      $this->mode = mcrypt_rc4;
    }
  }
 }
 /**
  * sets the key.
  *
  * keys can be between 1 and 256 bytes long. if they are longer then 256 bytes, the first 256 bytes will
  * be used. if no key is explicitly set, it'll be assumed to be a single null byte.
  *
  * @access public
  * @param string $key
  */
 function setkey($key)
 {
  $this->key = $key;
  if ( crypt_rc4_mode == crypt_rc4_mode_mcrypt ) {
   return;
  }
  $keylength = strlen($key);
  $keystream = array();
  for ($i = 0; $i < 256; $i++) {
   $keystream[$i] = $i;
  }
  $j = 0;
  for ($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->encryptindex = $this->decryptindex = array(0, 0);
  $this->encryptstream = $this->decryptstream = $keystream;
 }
 /**
  * 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 $iv
  * @see crypt_rc4::setkey()
  * @access public
  */
 function setiv($iv)
 {
 }
 /**
  * sets mcrypt parameters. (optional)
  *
  * if mcrypt is being used, empty strings will be used, unless otherwise specified.
  *
  * @link http://php.net/function.mcrypt-module-open#function.mcrypt-module-open
  * @access public
  * @param optional integer $algorithm_directory
  * @param optional integer $mode_directory
  */
 function setmcrypt($algorithm_directory = '', $mode_directory = '')
 {
  if ( crypt_rc4_mode == crypt_rc4_mode_mcrypt ) {
   $this->mcrypt = array($algorithm_directory, $mode_directory);
   $this->_closemcrypt();
  }
 }
 /**
  * encrypts a message.
  *
  * @see crypt_rc4::_crypt()
  * @access public
  * @param string $plaintext
  */
 function encrypt($plaintext)
 {
  return self::tohex($this->_crypt($plaintext, crypt_rc4_encrypt));
 }
 /**
  * decrypts a message.
  *
  * $this->decrypt($this->encrypt($plaintext)) == $this->encrypt($this->encrypt($plaintext)).
  * atleast if the continuous buffer is disabled.
  *
  * @see crypt_rc4::_crypt()
  * @access public
  * @param string $ciphertext
  */
 function decrypt($ciphertext)
 {
  $ciphertext = self::fromhex($ciphertext);
  return $this->_crypt($ciphertext, crypt_rc4_decrypt);
 }
 /**
  * encrypts or decrypts a message.
  *
  * @see crypt_rc4::encrypt()
  * @see crypt_rc4::decrypt()
  * @access private
  * @param string $text
  * @param integer $mode
  */
 function _crypt($text, $mode)
 {
  if ( crypt_rc4_mode == crypt_rc4_mode_mcrypt ) {
   $keystream = $mode == crypt_rc4_encrypt ? 'encryptstream' : 'decryptstream';
   if ($this->$keystream === false) {
    $this->$keystream = mcrypt_module_open($this->mode, $this->mcrypt[0], mcrypt_mode_stream, $this->mcrypt[1]);
    mcrypt_generic_init($this->$keystream, $this->key, '');
   } else if (!$this->continuousbuffer) {
    mcrypt_generic_init($this->$keystream, $this->key, '');
   }
   $newtext = mcrypt_generic($this->$keystream, $text);
   if (!$this->continuousbuffer) {
    mcrypt_generic_deinit($this->$keystream);
   }
   return $newtext;
  }
  if ($this->encryptstream === false) {
   $this->setkey($this->key);
  }
  switch ($mode) {
   case crypt_rc4_encrypt:
    $keystream = $this->encryptstream;
    list($i, $j) = $this->encryptindex;
    break;
   case crypt_rc4_decrypt:
    $keystream = $this->decryptstream;
    list($i, $j) = $this->decryptindex;
  }
  $newtext = '';
  for ($k = 0; $k < strlen($text); $k++) {
   $i = ($i + 1) & 255;
   $j = ($j + $keystream[$i]) & 255;
   $temp = $keystream[$i];
   $keystream[$i] = $keystream[$j];
   $keystream[$j] = $temp;
   $temp = $keystream[($keystream[$i] + $keystream[$j]) & 255];
   $newtext.= chr(ord($text[$k]) ^ $temp);
  }
  if ($this->continuousbuffer) {
   switch ($mode) {
    case crypt_rc4_encrypt:
     $this->encryptstream = $keystream;
     $this->encryptindex = array($i, $j);
     break;
    case crypt_rc4_decrypt:
     $this->decryptstream = $keystream;
     $this->decryptindex = array($i, $j);
   }
  }
  return $newtext;
 }
 /**
  * treat consecutive "packets" as if they are a continuous buffer.
  *
  * say you have a 16-byte plaintext $plaintext. using the default behavior, the two following code snippets
  * will yield different outputs:
  *
  * <code>
  * echo $rc4->encrypt(substr($plaintext, 0, 8));
  * echo $rc4->encrypt(substr($plaintext, 8, 8));
  * </code>
  * <code>
  * echo $rc4->encrypt($plaintext);
  * </code>
  *
  * the solution is to enable the continuous buffer. although this will resolve the above discrepancy, it creates
  * another, as demonstrated with the following:
  *
  * <code>
  * $rc4->encrypt(substr($plaintext, 0, 8));
  * echo $rc4->decrypt($des->encrypt(substr($plaintext, 8, 8)));
  * </code>
  * <code>
  * echo $rc4->decrypt($des->encrypt(substr($plaintext, 8, 8)));
  * </code>
  *
  * with the continuous buffer disabled, these would yield the same output. with it enabled, they yield different
  * outputs. the reason is due to the fact that the initialization vector's change after every encryption /
  * decryption round when the continuous buffer is enabled. when it's disabled, they remain constant.
  *
  * put another way, when the continuous buffer is enabled, the state of the crypt_des() object changes after each
  * encryption / decryption round, whereas otherwise, it'd remain constant. for this reason, it's recommended that
  * continuous buffers not be used. they do offer better security and are, in fact, sometimes required (ssh uses them),
  * however, they are also less intuitive and more likely to cause you problems.
  *
  * @see crypt_rc4::disablecontinuousbuffer()
  * @access public
  */
 function enablecontinuousbuffer()
 {
  $this->continuousbuffer = true;
 }
 /**
  * treat consecutive packets as if they are a discontinuous buffer.
  *
  * the default behavior.
  *
  * @see crypt_rc4::enablecontinuousbuffer()
  * @access public
  */
 function disablecontinuousbuffer()
 {
  if ( crypt_rc4_mode == crypt_rc4_mode_internal ) {
   $this->encryptindex = $this->decryptindex = array(0, 0);
   $this->setkey($this->key);
  }
  $this->continuousbuffer = false;
 }
 /**
  * dummy function.
  *
  * since rc4 is a stream cipher and not a block cipher, no padding is necessary. the only reason this function is
  * included is so that you can switch between a block cipher and a stream cipher transparently.
  *
  * @see crypt_rc4::disablepadding()
  * @access public
  */
 function enablepadding()
 {
 }
 /**
  * dummy function.
  *
  * @see crypt_rc4::enablepadding()
  * @access public
  */
 function disablepadding()
 {
 }
 /**
  * class destructor.
  *
  * will be called, automatically, if you're using php5. if you're using php4, call it yourself. only really
  * needs to be called if mcrypt is being used.
  *
  * @access public
  */
 function __destruct()
 {
  if ( crypt_rc4_mode == crypt_rc4_mode_mcrypt ) {
   $this->_closemcrypt();
  }
 }
 /**
  * properly close the mcrypt objects.
  *
  * @access prviate
  */
 function _closemcrypt()
 {
  if ( $this->encryptstream !== false ) {
   if ( $this->continuousbuffer ) {
    mcrypt_generic_deinit($this->encryptstream);
   }
   mcrypt_module_close($this->encryptstream);
   $this->encryptstream = false;
  }
  if ( $this->decryptstream !== false ) {
   if ( $this->continuousbuffer ) {
    mcrypt_generic_deinit($this->decryptstream);
   }
   mcrypt_module_close($this->decryptstream);
   $this->decryptstream = false;
  }
 }
 // @function fromhex 把十六进制数转换成字符串
 function tohex($sa , $len = 0){
  $buf = "";
  if( $len == 0 )
   $len = strlen($sa) ;
  for ($i = 0; $i < $len; $i++)
  {
   $val = dechex(ord($sa{$i}));  
   if(strlen($val)< 2) 
    $val = "0".$val;
   $buf .= $val;
  }
  return $buf;
 }
 // @function fromhex 把十六进制数转换成字符串 
 function fromhex($sa){
  $buf = "";
  $len = strlen($sa) ;
  for($i = 0; $i < $len; $i += 2){
   $val = chr(hexdec(substr($sa, $i, 2)));
   $buf .= $val;
  }
  return $buf;
 }
}

include('class.rc4crypt.php');
$rc4 = new crypt_rc4();
$rc4 -> setkey('21sd54a1w5q');
$text = 'www.jb51.net';
echo $x = $rc4->encrypt($text);//加密
echo '<br />';
echo $rc4->decrypt( $x) ;//解密