PHP information reversible encryption example sharing

This article mainly introduces the method of realizing reversible encryption in PHP, and draws on the encryption principle of discuz to realize the function of reversible encryption through keys. I hope to be helpful.

The details are as follows:

The encryption class introduced here can be reversed, and it is difficult to crack without a key.

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));
  }
}
?>

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