On Feb 5, 2005, at 5:55 AM, Michael Gebhart wrote:

> The user gets a code to activate some more features. In
> the code, there only is a flag reg=true/false. When the code is 
> entered,
> the application checks it and sets the variable to true, or false. The
> user can now take a look at my code and simply change this part. After 
> the
> check he sets: reg=true.

Bundle public keys for each unlockable feature and require a "key" to 
unlock it which is actually the signed name of the user (signed using 
the private key for the feature.

Cryptographically secure feature unlocking, with the side effect of 
letting you know the initial source (though possibly not purposeful) of 
any pirated versions.

-Brian