Hey,
I have been working professionally as a IOT software developer, with prime focus in C/C++ and python, I have experience developing core low-level software for raspi devices, I already have worked on something much similar to your requirement as a POC (except flashing unauthorized).
We can setup a cron/systemd service for handling periodic checking for authorisation.
I can implement everything from scratch in C++ (or python , no issues there), for hiding the source-code we can either directly use C++ or encode/encrypt python code, which makes it unreadable.
Software will run as daemon process and won't show up in ps -ef for that user (would require root permissions).
Note: If GUI interface is reqd. , no issues there but it will be a very minimalsitic interface (not very high-end frontend) , also if the admin will be entering the CPU symbol number of that device only, then we can directly handle it without admin interaction and automate the entire process.
I have raspi3 in hand for testing, so it won't be an issue as Rpi version doesn't matter in this project.
Please dm if interested.
Thanks