There's an esphome config for them and esphome let's you set a password. I believe it supports encryption but I can't remember.
The faikins are really awesome. I have mine set up in Home Assistant and I have automations for them to do stuff to turn off if the outdoor and indoor temps are both pleasant. I also have it set up to turn off if any of my windows or exterior doors are left open for more than five minutes. But you can program them to do so much. The stock firmware does mqtt so it's quite versatile.
These things are great, I've managed to get them into all my indoor units without too much trouble. If you've already got them integrated into Home Assistant check out Versatile Thermostat (you can find it in HACS), if you've got temp sensors in the rooms with your AC you'll get very good target temperature tracking, much better than the auto functionality built into Faikin.
The faikins are really awesome. I have mine set up in Home Assistant and I have automations for them to do stuff to turn off if the outdoor and indoor temps are both pleasant. I also have it set up to turn off if any of my windows or exterior doors are left open for more than five minutes. But you can program them to do so much. The stock firmware does mqtt so it's quite versatile.