Upper Bounds of Differential Characteristic Probability for Unbalanced Feistel Network Employing DSM

摘要

In this paper,for the unbalanced Feistel network which employs diffusion matrices in a switching way,we study the fixed number of its differential active S-boxes.Firstly we obtain some lower bounds of the differential active S-boxes for m,2m and 3m rounds of Feistel structure,respectively.By concatenating these rounds,a fixed number of differential active S-boxes for arbitrary round number is derived.Our results imply that the unbalanced Feistel network using DSM is more secure than the traditional structure.