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：
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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;
}
}
使用方法：
setKey('21sd54a1w5q');
$text = 'www.jb51.cc';
echo $x = $rc4->encrypt($text);//加密
echo '
'; echo $rc4->decrypt( $x) ;//解密
'; echo $rc4->decrypt( $x) ;//解密
运行结果：
7907bb7c6694f179e9642ebd www.jb51.cc
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》希望本文所述对大家PHP程序设计有所帮助。
