Best place to hide a key in the Windows Registry?

Question

My Delphi program has a built-in protection mechanism to check for banned license keys on the Internet and displays a message to the user if a blacklisted key is found.

Answer 1

It will be very challenging to achieve what you're trying to do, since a user can simply uninstall and re-install, and savvy users can wipe all traces of your app from the system (including the registry).

Other apps (like Windows, for example), instead of checking for a negative (banned key), instead check for a positive (good key). You "activate" the software once (when connected online) and this activation stores the "good key", which you can then check for whenever running the software (whether online or offline).

I'd suggest the second approach for you.