"Change Set: AES
Date: 24 November 2006
Author: Timothy J. Miller
Refactored as a single class and did away with the factory method.
Don't know what I was thinking there. New Error subclass to raise when
attempting to do something valid in Rijndael that AES doesn't allow.
Created Cryptography-Exceptions category as something tells me that this
won't be the last exception."!