THE RESEARCH OF Rijndael

The block cipher is one of the two aspects of the modern applied cryptography systems. It has some characteristics - the fast speed, the easy standardization, convenient implement by software and hardware, and so on. The block cipher always is the main parts of the data encryption, digital signature, authentication and key management in the security of information and network. So it is used in wide range either in the security area of the computer communication or in the security area of the information system.The design and the analysis of the block cipher not only are contrary but also are dependent each other. And the contradiction between them promotes the fast development in the block cipher.This paper is discussed with respect to these two aspects. In this paper , at fist, the design architecture of DES and the two famous cryptanalysis which are the differential cryptanalysis and the linear cryptanalysis for analysising DES primarily are introduced , especially Rijndael as the new advanced encryption standardization . And more , the lastest trends about the algorithm of the block cipher also is kept close watch on. Second, the selection principles of AES and the other four candidate algorithms resumptively are introduced. After seriously learning the five candidate algorithms, the ways or algorithms that we compute the reverse of a polynomial in the different fields in Rijndael are advanced, while the S-box and the reverse of it also are provided. By studying the key schedule of Rijndael, a new key schedule is put forward and executed by ANSI C implement.