public function setExtra($extra)
    {
        if (isset($extra['secret']) && strlen($extra['secret']) > 17) {
            $extra['secret'] = hex2bin($extra['secret']);
        }
        if (isset($extra['secret']) && strlen($extra['secret']) == 17) {
            $extra['secret'] = substr($extra['secret'], 0, 16);
        }
        $this->extra = $extra;
    }