Fast Implementation And Security Analysis Of AES

With the rapid development of computer and communication technology, designing analyzing block cipher uses widely and researches deeply. At present, there are a lot of research achievements in the field of block cipher. Especially, the Rijndael algorithm should be considered the excellent representative of all the researches. When the data encryption standard was replaced by the advanced encryption standard, the whole world is putting light on the Rijndael algorithm.The study of implement and cryptanalysis of the Rijndael in this paper contains three parts. Firstly, with research in the Rijndael algorithm, it puts forward the proposal of a high-speed implementation of Rijndael basing on 32-bit platform. By analyzing the characteristic of each round operation, combine and simplify the inner processes, and the Rijndael can be implemented by shifting, xor and looking up tables. In additional, expanding all the operation in advance is propitious to higher implementation.Secondly, the S box of the Rijndael has short iterative cycle which will become the deadly weakness, because any plain text and differential of plain text will revert to type when it transforms 16 times through linear diffuse layer. With the study of the S box and affine transformation, 100 pairs of (u, v) was found, whose iterative cycle of S box is 256. By analyzing the cryptography property of the S box given birth to the pair of (241, 21) and the S box of Rijndael, it is found that the S box given birth to the pair of (241, 21) performs more excellently than the S box of Rijndael. Therefore, the designer should consider the iterative cycle of S box , when he design a S box.Finally, after studying the Square Cryptanalysis which is the most effective way to attack the reduced Rijndael, it gives 4 to 5 rounds Square Cryptanalysis'soft implementation. In this paper, it uses the distributed concept to optimize the implementation of Square-5, so it takes less time to find out a cipher key. It spends 10 days to recover a right key by using just one computer while it only needs 2.5days to recover a right key by using four computers. This shows that the distributed concept can also to optimize the implementation of Square Cryptanalysis more than 5 rounds.