I have yet to see a game that protects secrets from datamining by encrypting game assets with a key that is the solution to an in-game puzzle.

For instance, you enter a password into a locked door and the password is used to decrypt 3D objects, text, scripts, etc. that lie behind the door.

The main problem is that the password needs to be fairly long/complex to resist brute force, so it might be a bit annoying to enter in-game.