End-User App Licensing

[Martin Obongita]

Shalom Omnis Dudes,
This is a strange request, or so it seems.
Could anyone share a snippet of how to code the registration process of an app?
I am thinking of the app generating random numbers to the end-user.The user relays those numbers back.
I generate corresponding numbers to validate the user's registration number to validate the app.
Kind regards,Martin Obongita.