中纪委app内容加密分析

api Android 逆向

function decrypt($str){
    $len = strlen($str);
    $decrypt_str=array();
    for ($x=0; $x<$len; $x++) {
        $c = $str[$x];
        if ($c == 'A') {
          $c = 'Z';
        } else if ($c == 'a') {
          $c = 'z';
        } else if ($c == '0') {
          $c = '9';
        } else if (('A' < $c && $c <= 'Z') || (('a' < $c && $c <= 'z') || ('0' < $c && $c <= '9'))) {
          $c =  chr(ord($c) - 1);
        }
        array_push($decrypt_str, $c);
    }
    $str_decrypt = base64_decode(implode("", $decrypt_str));
    return $str_decrypt;
}