@H_403_0@本文实例讲述了PHP实现的rc4加密解密类。分享给大家供大家参考，具体如下：

• 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,'');
  }
  $newText = mcrypt_generic($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:
• echo $rc4->encrypt(substr($plaintext,8));
• echo $rc4->encrypt(substr($plaintext,8,8));
• echo $rc4->encrypt($plaintext);
• The solution is to enable the continuous buffer. Although this will resolve the above discrepancy,it creates
• another,as demonstrated with the following:
• $rc4->encrypt(substr($plaintext,8));
• echo $rc4->decrypt($des->encrypt(substr($plaintext,8)));
• echo $rc4->decrypt($des->encrypt(substr($plaintext,8)));
• 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;
  }
  }