Didier Stevens made a funny little find in Windows 7. In the past, userassist keys had been encrypted in ROT13. Now, he sees them encrypted in a Vigenère cipher.
(In case you’re not familiar with these terms, ROT13 is trivial to crack, and Vigenère, although quite a bit more sophisticated than ROT13, is breakable, so it seems just to be a little bit of fun on the part of the developers at Microsoft with the crypto community — sort of an Easter Egg of sorts).
Nice find Didier!