php5数字型字符串加解密代码

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<?php
/* ----------------------------------------------------------------------------
* Script Name: encrypt.php
* Creation Date: 2008-4-7 10:36
* Last Modified: 2008-4-12 16:00
* Author: meyu
* Copyright (c) 2007
* Purpose: 数字字符串简易加解密
* ----------------------------------------------------------------------------*/

class Encryption {
/**
* 最终的密文代码，可设为任意不重复的10位英文字符a-zA-Z
*/
private $replacement = 'urskydMeIV';

/**
* 增加的密文第一位，可设为1位除0以外的整数，即 1-9
*/
private $prefix = "8";

/**
* 公钥,长度小于8位的正整数
*/
private $match = "111111";

/**
* 转换后对照数组
*/
private $replaceenc;
private $replacedec;

function __construct() {
for($i =0; $i < 10; $i++) {
$this->replaceenc['/'.$i.'/'] = $this->replacement{$i};
$this->replacedec['/'.$this->replacement{$i}.'/'] = $i;
}
}

public function encrypt($str) {
return preg_replace(
array_keys($this->replaceenc),
$this->replaceenc,
$this->mynotin(preg_replace("/(.)(.)/", "${2}${1}", $str))
);
}

public function decrypt($str) {
return preg_replace("/(.)(.)/", "${2}${1}",
$this->mynotout(preg_replace(array_keys($this->replacedec),$this->replacedec,$str))
);
}

private function mynotin($str) {
$str_out = "";
$i = 0;
while(isset($str{7*$i})) {
$str_out .= (($this->prefix.substr($str, $i*7, 7))+0)^$this->match;
$i++;
}
return $str_out;
}

private function mynotout($str) {
$str_out = "";
$i = 0;
while(isset($str{8*$i})) {
$str_out .= substr((substr($str, $i*8, 8)+0)^$this->match, 1);
$i++;
}
return $str_out;
}
}
?>

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