如何将高效加密解密函数改写为支持超长密钥输入的？

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使用核心代码实现Discuz!加密，支持加密和解密，双向功能。自定义失效时间，函数如下：

phpfunction authcode($string, $operation='DECODE', $key='', $expiry=0) { $ckey_length=4; $key=md5($key !='' ? $key : 'AUTH_KEY'); $keya=md5(substr($key, 0, 16)); $keyb=md5(substr($key, 16, 16)); $keyc=$keya; $cryptkey=$keyc.$keyb; $encryptkey=md5($cryptkey); $iv=md5(substr($encryptkey, 0, 16)); if ($operation=='DECODE') { $decode=openssl_decrypt($string, 'AES-128-CBC', $encryptkey, OPENSSL_RAW_DATA, $iv); if ($decode && substr($decode, 0, 16)==substr(md5($keyc.$keyb), 0, 16)) { return substr($decode, 16); } } else { $time=time(); $expire=$time + $expiry; $string=$expire.'|'.substr(md5($string.$keyb), 0, 16).$string; $string=$keya.substr(md5($keya.$string.$keyb), 0, 16).$string; $string=openssl_encrypt($string, 'AES-128-CBC', $encryptkey, OPENSSL_RAW_DATA, $iv); return $string; }}

核心代码来自discuz，可加密，可解密，是双向的
可定义失效时间

function authcode($string, $operation = 'DECODE', $key = '', $expiry = 0) { $ckey_length = 4; $key = md5($key != '' ? $key : C('AUTH_KEY')); $keya = md5(substr($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($result, 26).$keyb), 0, 16)) { return substr($result, 26); } else { return ''; } } else { return $keyc.str_replace('=', '', base64_encode($result)); } }