On Generalized Feistel Structures Using the Diffusion Switching Mechanism

概要

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To design secure blockciphers, estimating immunity against differential attack and linear attack is essential. Recently, Diffusion Switching Mechanism (DSM) is proposed as a design framework to enhance the immunity of Feistel structure against differential attack and linear attack. In this paper, we give novel results on the effect of DSM on three generalized Feistel structures, i. e. Type-I, Type-II and Nybergs structures. We first show a method for roughly estimating lower bounds of a number of active S-boxes in Type-I and Type-II structures using DSM. Then we propose an improved search algorithm to find lower bounds for generalized structures efficiently. Experimental results obtained by the improved algorithm show that DSM raises lower bounds for all of the structures, and also show that Nybergs structure has the slowest diffusion effect among them when SP-type F-functions are used.
（社）電子情報通信学会の論文
2008-08-01