I wanted to describe it the other day, but I was discouraged because of the behavior of holycows.
What you describe, sounds like a bank's security code generator systems, which comes in variety.
One you described is like: You download an app to your personal device (in this case device can be onboard/offboard computer) using personal id, you end up having your personal/unique app. connected to your device and account. Now every time you need to login, you contact certain secure site, which generate QR code on screen, which you shall scan using your personal device having personal/unique app, if all matches, than your personal device receive a numeric code, which is generated by an automated code generator SW, which you (pilot) will enter to login. In case of bank account, by default there are limits over online transactions, however you may ask for changes, but you see no difference in login process. Basically a code can have limits hidden in it, which basically are in control of your bank.
There is another commonly known tech. used by companies to restrict ''unauthentic access'' or allow ''licensed access'' to its HW/SW.
Why its needed: Since all hitech electronic HW is manufactured in China, which was designed/developed in EU/US. If there's no lock, you will soon see a Chinese/Indian version of it.
Trick is to have a mix of HW-SW key (aka-dongle) this HW key will be programmed as having unique code id (as an example: code is generated at company's head office and keys are programed subsequently).
Now when proprietary hitech HW is loaded with proprietary SW, it will not perform certain tasks and limits the performance of machine, or not perform at all, unless a matching code is written in its SW, which again can be with aid of special interface or simple keyboard, but it effectively kicks out the owner of HW of having any control over its property. This prevents ''unauthorized'' use of tech. but if I'm not in good terms with ''authorized'' user, manufacturer of HW can just declare ''authorized'' user as rouge element/state and multi billion $ HW is as good as trash.
Another common one, we all know is GPS triggered car immobilizers.
Now these are commonly known and widely used 'kill switches' we come across daily, where limit is defined by manufacturer of HW.
