if err != nil {
			return nil, err
		}
		client = kes.NewClientWithConfig("", &tls.Config{
			MinVersion:         tls.VersionTLS12,
			Certificates:       []tls.Certificate{cert},
			RootCAs:            config.RootCAs,
			ClientSessionCache: tls.NewLRUClientSessionCache(tlsClientSessionCacheSize),
		})
	} else {
		client = kes.NewClientWithConfig("", &tls.Config{
			MinVersion:         tls.VersionTLS12,