private function configure()
    {
        $keyCert = SignatureUtils::generateKeyCert($this->settings);
        $dir = dirname($this->settings['sp_key_file']);
        if (!is_dir($dir)) {
            throw new \InvalidArgumentException('The directory you selected for sp_key_file does not exist. Please create ' . $dir);
        }
        $dir = dirname($this->settings['sp_cert_file']);
        if (!is_dir($dir)) {
            throw new \InvalidArgumentException('The directory you selected for sp_cert_file does not exist. Please create ' . $dir);
        }
        file_put_contents($this->settings['sp_key_file'], $keyCert['key']);
        file_put_contents($this->settings['sp_cert_file'], $keyCert['cert']);
    }