Two New Methods for Designing 192-bit Block Ciphers Based on Switching Structure and Recursive Diffusion Layers

In recent years, compared with stream ciphers more attention has been to block ciphers because of their proved security and wide application. Design of most block ciphers are based on substitution-permutation network (SPN) or Fiestel structure. Although Fiestel structures compared with SPN has many benefits, but since they have less active S-boxes in round function, it has a security weakness. In this paper, we introduce two new methods for designing 192-bit block cipher algorithms that use Switching Structure and Recursive Diffusion Layers to increase active S-boxes. The first method is based on switching structure and 3×3 multiple Recursive Diffusion Layers and the second method used switching structure and 2×2 multiple Recursive Diffusion Layers. Security of tow structures using linear programming offered analysed with linear programming and evaluated the results show of resistance to linear and differential cryptoanalysis. Also, since the Recursive Diffusion Layers are more efficient than MDS matrices in software and hardware, thus designed algorithms with these methods have high performance in various platforms.