The method and principle of reversible encryption in PHP

This article mainly introduced the PHP reversible encryption method and the principle, the interest friend's reference, hoped to be helpful to everybody.

The PHP code is as follows:

<?phpclass 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 original text or ciphertext * @param string $operation operation (ENCODE |  DECODE), default is DECODE * @param string $key key * @param int $expiry ciphertext expiration, encryption time valid, unit seconds, 0 is permanent valid * @return The original text after string processing or after Base64_encode processed ciphertext * @example * $a = authcode (' abc ', ' Encode ', ' key '); * $b = Authcode ($a, ' DECODE ', ' key '); $b (ABC) * * $a = authcode (' abc ', ' ENCODE ', ' key ', 3600); * $b = Authcode (' abc ', ' DECODE ', ' key ');  Within one hours, $b (ABC), otherwise $b is empty */function authcode ($string, $operation = ' DECODE ', $key = ' ', $expiry =0) {$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 = = ' DECODE '? substr ($string, 0, $ckey _length): substr (MD5 (Microtime ()),-$ckey _length)): ";  $cryptkey = $keya. MD5 ($keya. $KEYC);  $key _length=strlen ($cryptkey); $string = $operation = = = ' DECODE '? Base64_decode (substr ($string, $ckey _length)): sprintf ('%010d ', $expiry? $expiry +time (): 0). substr (MD5 ($string. $keyb  ), 0,16). $string; $string _lengtH=strlen ($string);  $result = ";  $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 ($operation = = ' DECODE ') {if (substr ($result, 0,10) ==0| |      substr ($result, 0,10)-time () >0) &&substr ($result, 10,16) ==substr (MD5 (substr ($result, up). $keyb), 0,16)) {    Returnsubstr ($result, 26);    }else{return ';  }}else{return $KEYC. Str_replace (' = ', ' ', Base64_encode ($result)); }}?>

Summary: the above is the entire content of this article, I hope to be able to help you learn.

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