public function getMacKey()
    {
        $key = $this->config['key'];

        $hexStrKey = substr($key, 0, 38);
        $hexFinal = "" . substr($key, 38, 2) . "00";

        $cca0 = ord($hexFinal);

        if ($cca0 > 70 && $cca0 < 97) {
            $hexStrKey .= chr($cca0 - 23) . substr($hexFinal, 1, 1);
        } else {
            if (substr($hexFinal, 1, 1) == "M") {
                $hexStrKey .= substr($hexFinal, 0, 1) . "0";
            } else {
                $hexStrKey .= substr($hexFinal, 0, 2);
            }
        }

        return pack("H*", $hexStrKey);
    }