10/20/2017 (Fri) 16:22:07
Not secure at all. In the age of ipv6 networks it would become even worse, see how Shodan discovered vulnerable iot devices with rogue ntp servers. And with current state of TLS, you trust certificate authorities on keeping your traffic encrypted, 2 third parties involved already.
Better, but do not expose full positioning shell to the system, i.e. like how it is done in smartphones. Only get time signal. Extra points if you find actual military device that accepts encrypted and signed satellite signal.
Finally, add a few terrestrial radio synchronization receivers for maximum failproof. General rule of thumb for computers would be to keep real-time clock running and if the synchronization offset is too big, then something is happening and they should keep the old time setting.