The Rijndael block cipher (AES proposal) : a comparison with DES

In October 2000, after three years of competition between 15 candidate algorithms, the National Standards and Technology (NIST) chose the Rijndael algorithm to be adopted as Advanced Encryption Standard (AES) by the U.S. Department of Commerce, replacing to Data Encryption Algorithm (DES), which has been the standard since 1977. The authors analyze the structure and design of new AES, following three criteria: a) resistance against all known attacks; b) speed and code compactness on a wide range of platforms; and c) design simplicity; as well as its similarities and dissimilarities with other symmetric ciphers. On the other side, the principal advantages of new AES with respect to DES and T-DES, as well as its limitations, are investigated. Thus, for example, the fact that the new cipher and its inverse use different components, which practically eliminates the possibility for weak and semi-weak keys, as existing for DES, and the non-linearity of the key expansion, which practically eliminates the possibility of equivalent keys, are two of the principal advantages of new cipher. Finally, the implementation aspects of Rijndael cipher and its inverse are treated. Thus, although Rijndael is well suited to be implemented efficiently on a wide range of processors and in dedicated hardware, we have concentrated our study on 8-bit processors, typical for current smart cards and on 32-bit processors, typical for PCs.