Thats exactly the section i was referring to. I understand the importance of randomizing the start and end of the transmission, i've used that principal before in adding salt/pepper to encryption, what i dont understand is how this helps in this instance. Yes, you've created a unique message every time, but does your receiver store all the messages and checks to see this message hasn't been received in the past? otherwise what stops an attacker from recording the "1;1;1;0;47;uKvGG7z440r/1pln4IJbNQ==" you've sent, and then repeating it? the receiver will still decrypt it as a viable code.
The nrf52840 look really nice, but might be a bit challenging for my soldering skills. If all i want is a low power wireless lock, i can call it a day with just either of these units (1, 2) for both processing and transmission, 2 AA batteries without a regulator, and the motor?