August 25th, 2011, 10:26 AM
AES Encryption Query
As part of my degree I am learning about AES encryption, I understand the operations(i think) but it has yet to properly 'click' for me to feel like I fully understand it. One thing I am pondering at the moment is why are the operations(SubBytes, ShiftRows, MixColumns, and Add round key) done in the order they are? What happens if you did them in a different order? Would it produce a lower level of security?
Help would be very much appreciated!
August 26th, 2011, 07:04 PM
That really is a Mathematics question. I have not studied it recently, but I am pretty sure that the order is important and helps with many known attacks.
Its well documented that the "S-box" used by DES were carefully designed to prevent a differential attack -- this was put in years before the existence of differential attacks was known in published research.