Impossible Differential Characteristics of Extended Feistel Networks with Provable Security against Differential Cryptanalysis

Abstract

AbstractThe design of block ciphers with provable security against differential and linear cryptanalysis has always been an important consideration. However, it is also vital to evaluate the security of block ciphers against other forms of cryptanalysis, for example, impossible differential cryptanalysis, a variant of differential cryptanalysis (DC). In impossible differential cryptanalysis, impossible differential characteristics are used to retrive a subkey material for the first or the last several rounds of block ciphers. Thus the security of a block cipher against impossible differential cryptanalysis can be evaluated by impossible differential characteristics [1]. In this paper, we will first examine the security of Extended Feistel Networks (EFN) against DC and then use the U-method introduced in [1] to find impossible differential characteristics of EFN.KeywordsDifferential CryptanalysisExtended Feistel NetworksImpossible Differential Characteristics