Comment by dns_snek

> Authentication is hard.

Authentication is easy, getting people (esp. leadership) to give a shit is hard.

Control loop is obviously local and performed by dedicated controller hardware. If you only need remote monitoring then don't expose any management functionality.

If you want remote management, then define an envelope of allowable system parameters that can be controlled remotely. Allowing defrost to be initiated remotely has obvious risks and known solutions - add a hardware interlock, like a physical button or a key switch.

Even if you ignore all other precautions and allow all parameters to be controlled without limitations, strong authentication is still easy to implement, if anyone cares enough to do it.