PHP reversible encryption methods and principles

This article mainly introduces the methods and principles of PHP reversible encryption. Interested friends can refer to it. I hope it will be helpful to everyone.

The PHP code is as follows:

<?php
class encryptCalss
{
var $key=12;
function encode($txt){
for($i=0;$i<strlen($txt);$i++){
$txt[$i]=chr(ord($txt[$i])+$this->key);
}
return $txt=urlencode(base64_encode(urlencode($txt)));
}
function decode($txt){
$txt=urldecode(base64_decode($txt));
for($i=0;$i<strlen($txt);$i++){
$txt[$i]=chr(ord($txt[$i])-$this->key);
}
return $txt;
}
}
?>

discuz encryption and decryption:

<?php
/**
 * 
 * @param string $string 原文或者密文
 * @param string $operation 操作(ENCODE | DECODE), 默认为 DECODE
 * @param string $key 密钥
 * @param int $expiry 密文有效期, 加密时候有效， 单位 秒，0 为永久有效
 * @return string 处理后的 原文或者 经过 base64_encode 处理后的密文
 * @example 
 *  $a = authcode(&#39;abc&#39;, &#39;ENCODE&#39;, &#39;key&#39;);
 *  $b = authcode($a, &#39;DECODE&#39;, &#39;key&#39;); // $b(abc)
 * 
 *  $a = authcode(&#39;abc&#39;, &#39;ENCODE&#39;, &#39;key&#39;, 3600);
 *  $b = authcode(&#39;abc&#39;, &#39;DECODE&#39;, &#39;key&#39;); // 在一个小时内，$b(abc)，否则 $b 为空
 */
function authcode($string,$operation=&#39;DECODE&#39;,$key=&#39;&#39;,$expiry=0){
  $ckey_length=4;
  $key=md5($key ? $key:"kalvin.cn");
  $keya=md5(substr($key,0,16));
  $keyb=md5(substr($key,16,16));
  $keyc=$ckey_length ? ($operation==&#39;DECODE&#39; ? substr($string,0,$ckey_length):substr(md5(microtime()),-$ckey_length)):&#39;&#39;;
  $cryptkey=$keya.md5($keya.$keyc);
  $key_length=strlen($cryptkey);
  $string=$operation==&#39;DECODE&#39; ? base64_decode(substr($string,$ckey_length)):sprintf(&#39;%010d&#39;,$expiry ? $expiry+time():0).substr(md5($string.$keyb),0,16).$string;
  $string_length=strlen($string);
  $result=&#39;&#39;;
  $box=range(0,255);
  $rndkey=array();
  for($i=0;$i<=255;$i++){
    $rndkey[$i]=ord($cryptkey[$i%$key_length]);
  }
  for($j=$i=0;$i<256;$i++){
    $j=($j+$box[$i]+$rndkey[$i])%256;
    $tmp=$box[$i];
    $box[$i]=$box[$j];
    $box[$j]=$tmp;
  }
  for($a=$j=$i=0;$i<$string_length;$i++){
    $a=($a+1)%256;
    $j=($j+$box[$a])%256;
    $tmp=$box[$a];
    $box[$a]=$box[$j];
    $box[$j]=$tmp;
    $result.=chr(ord($string[$i]) ^ ($box[($box[$a]+$box[$j])%256]));
  }
  if($operation==&#39;DECODE&#39;){
    if((substr($result,0,10)==0||substr($result,0,10)-time()>0)&&substr($result,10,16)==substr(md5(substr($result,26).$keyb),0,16)){
      returnsubstr($result,26);
    }else{
      return&#39;&#39;;
    }
  }else{
    return $keyc.str_replace(&#39;=&#39;,&#39;&#39;,base64_encode($result));
  }
}
?>

Summary: The above is the entire content of this article , I hope it can be helpful to everyone’s study.

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