CS 4363 -- Spring 2007 -- Lecture 4 Notes

CS 4363, Spring 2007
Lecture 4 Notes, 19 April 2007
AES characteristics and implementation

References:

Laws of Cryptography, Section VI, Chapters 19 - 24, Pages 114 - 138 [PDF, 1.1MB].
Rewrite of the AES Specs (Rijndael) by Brian Gladman [PDF, 280KB].

Simple Observations:

An algorithm that occasionally gives an answer is useless, but if such an algorithm is used for cryptanalysis, it makes the cryptosystem useless.
"Fancy" crypto uses "elegant" algorithms. Then there may be an elegant way to break them.
"Standard" crypto, like the AES, is not elegant, so there should be no elegant way to break it.

Using Logs to Multiply:

See Laws, pages 122-126.

Intro to the AES:

Table of "Sizes". See Laws, page 116.
"Word" = 4 bytes = 32 bits.
AES state: 4-by-4 byte 2-dim array.
AES algorithm outline. See Laws, pages 116-117.
AddRoundKey. See Laws, pages 130-132.
SubBytes. See Laws, pages 127-129.
ShiftRows. See Laws, page 133.
MixColumns. See Laws, pages 133-134.

Revision date: 2007-04-23. (Please use ISO 8601, the International Standard.)