Optimization Study of Rijndael Algorithm

Through analyzing the algorithm of Rijndael,some technical points are made in this paper with respect to improving several steps which may incur potential risks.By optimizing the most vulnerable MixColumns,the multiplication in field is replaced with using look-up tables so the security of nonlinearity is enhanced.In regard to creating the sub-key,instead of utilizing the simple linear selection as used in the original algorithm,this paper introduces the random function to generate and choose the keys so that the attacks of linear cryptanalysis can be resisted much more effectively.