Best practices for license key files

[Bill Vlahos]

I'm about to release a consumer application that has a license key.  
Since it will work on multiple platforms (thanks to Rev) I am planning  
on creating a license key file on disk so that all of the executables  
can use it.

The file will only contain 2 strings that make up the 2 parts of the  
key although there could be other descriptive text in the file too.  
The nature of this software is to be portable so it will be OK for the  
user to have the key file on multiple devices.

It could be as simple as a text file with the clear text strings on  
each line, or an XML file, or could be in a stack file, or the  
information could be encrypted (or otherwise processed in a way that  
makes it not clear text).

The two strings will be known to the user and they have to be a  
matched set or they won't be valid. I was just thinking of keeping it  
simple and just put them into a text file. I'm not that worried about  
piracy (at this point anyway) so knowing the information won't be that  
different than having a copy of the actual key file.

I'd be interested in what you folks do and the rational behind it.

Thanks,
Bill Vlahos