PHP source code Analysis of DZX1.5 encryption and decryption function Authcode usage

This article describes the PHP source code analysis of the DZX1.5 encryption and decryption function Authcode usage. Share to everyone for your reference. The specific analysis is as follows:

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<?php $authkey = ';/** * @param string $string: Entered plaintext (or ciphertext) that requires encryption (or decryption) * @param stri ng $operation: ' DECODE ' or other, where the default is to decrypt, enter other means of encrypting * @param string $key: Encryption key * @param int $expiry: validity/function Authcode ($s Tring, $operation = ' DECODE ', $key = ', $expiry = 0) {global $authkey; $ckey _length = 4; $key = MD5 ($key!= "? $key: $authkey); $keya = MD5 (substr ($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 < 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,) = 0 | | substr ($result, 0)-time () > 0) && subst R ($result) = = substr (MD5 (substr ($result,). $keyb), 0) {return substr ($result);} else {return ';}} else {return $KEYC. Str_replace (' = ', ', Base64_encode ($result));} $STR = ' 1234 '; $key = ' 1234 '; echo "PlainText:". $str; echo "<br/>"; echo "key:". $key; $encode = Authcode ($str, ' one ', $key); echo "<br/>"; echo "Encrypted ciphertext:". $encode; echo "<br/>"; $decode = Authcode ($encode, ' decode ', $key); echo "decrypted plaintext:". $decode; /*end of php*/

The results of the operation are as follows:

Clear text: 1234

Key: 1234

Encrypted ciphertext: A52F67EXZGVY0HTQBO4VOREHQ3WXNL6E2ZLX75JGFOJW

Decrypted plaintext: 1234

I hope this article will help you with your PHP program design.