I have simple secure (I guess) `Mosquitto` sever described in my [previous question][1].

Client machine has no any keys or certificate installed except single ca.crt certificate file generated and taken from `Mosquitto` server.

Is it possible that request performed by simple `MQTT` client below is encrypted and secure? 

 mosquitto_sub -h 192.168.1.8 -t sensor --cafile ca.crt -p 8883 -d

This client uses only single certificate file and no keys. Is it somehow possible encrypt traffic by having only certificate and no keys?

 [1]: https://unix.stackexchange.com/questions/557702/ensure-tls-communication-security-in-mosquitto/557705#557705