Serial Number Generator

Class to perform serial number generation, and checking, useful for registering shareware. Some time ago I was searching for a serial number generator here in PSC, since I couldn't find a good one, I decided to make it one by myself... The algorithm isn't the best in security but try to break a serial without looking to the code first... This is my first submission to PSC, it was time to give back :). Please, rate it, i would like to know your opinion