Maybe you should try a ready-made licensing system? Try ready-made DRM-systems (Digital rights management). You can find a lot of information on Wikipedia. Ther

Maybe you should try a ready-made licensing system? Try ready-made DRM-systems (Digital rights management). You can find a lot of information on Wikipedia. There are examples of free and paid programs. Also, you can use a ready-to-use key-making tool. ArmDot for example. As usual, such programs are paid. But maybe you can find something free on the GitHub. Good luck!