php源码分析之DZX1.5加密解密函数authcode用法

<?php$authkey = '';/** * @param string $string: 输入的需要加密（或解密）的明文（或密文） * @param string $operation: 'DECODE'或其它，其中默认表示解密，输入其它表示加密 * @param string $key: 加解密密钥 * @param int $expiry: 有效期 */function authcode($string, $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.$keyb), 0, 16).$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));  }}$str = '1234';$key = '1234';echo "明文:".$str;echo "<br />";echo "密钥:".$key;$encode = authcode($str,'11',$key);echo "<br />";echo "加密后的密文:".$encode;echo "<br />";$decode = authcode($encode,'DECODE',$key);echo "解密后的明文:".$decode;/*End of php*/