Classic PHP Cryptographic decryption function authcode () fix code, encrypt decrypt authcode_php tutorial

Classic PHP Cryptographic decryption function Authcode () repair code, encryption decryption Authcode

Authcode This function is used by many people, this function from the Discuz program, used to encrypt and decrypt the string, you can set the key (key) and expiration time, in many cases it is useful. The original function code may generate characters such as +,/, &, resulting in the retrieval of value via URL being escaped, resulting in an inability to decrypt. A little modification of the fire-side network, to replace these characters with other characters, decryption and then replace back, so it is perfect!

The code is as follows:

function Authcode ($string, $operation = ' DECODE ', $key = ", $expiry = 0) {if ($operation = = ' DECODE ') {$string = Str_rep Lace (' [a] ', ' + ', $string); $string = Str_replace (' [b] ', ' & ', $string); $string = Str_replace (' [C] ', '/', $string); } $ckey _length = 4; $key = MD5 ($key? $key: ' Livcmsencryption '); $keya = MD5 (substr ($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, (+). $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 <; $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, ten) = = 0 | | substr ($result, 0,)-time () > 0) && Subs  TR ($result, ten, +) = = substr (MD5 (substr ($result, $keyb), 0, +)) {return substr ($result, 26);  } else {return '; }} else {$ustr = $keyc. Str_replace (' = ', ' ', Base64_encode ($result)); $ustr = str_replace (' + ', ' [a] ', $ustr); $ustr = Str_r Eplace (' & ', ' [b] ', $USTR);  $ustr = Str_replace ('/', ' [C] ', $USTR); return $ustr; }}

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