protected function getAdapter()
    {
        $type = strtolower($this->options['type']);
        if (!$this->adapter) {
            if ($this->options['class']) {
                $adapterClass = $this->options['class'];
            } else {
                $adapterClass = '\\Wslim\\Security\\Crypt\\' . ucfirst($type) . 'Adapter';
            }
            
            if (!class_exists($adapterClass)) {
                throw new Exception('crypt type is not exists: ' . $type . ' .');
            }
            $this->adapter = new $adapterClass();
        }
        return $this->adapter;
    }