AES encryption

[Tuvas]

I have just finished a new function that will do AES128 encryption,
which is the standard for private-key cryptology today. In fact, the
NSA permitted AES to be used for classified documents in the USA, the
first time a public algorithm has been given this honor (Secret and Top
Secret documents can use AES as well, but must use a larger key (192 or
256 bits)) I've tested my function with a thousand random texts, it
seems to return the same result as received every time.

If you want to take a look,
http://www.geocities.com/brp13/Python/index.html

Note, I still wouldn't quite encrypt your credit card numbers, but,
well, it does seem to be secure enough... I would like comments as to
anything fairly simple I might be able to do to increase security. I've
tested the algorithm about a thousand times, with no appearant
failures, but, there still could be one that I haven't found yet, so...
Thanks!