Impossible Differential Evaluations for New-Structure Series

Impossible differential cryptanalysis is a powerful tool to evaluate the strength of a block cipher structure, and the key step of this cryptanalysis is to find the longest impossible differential. Recently a series of generalized Feistel structures named New-structure Ⅰ, Ⅱ, Ⅲ and Ⅳ were proposed, which were designed with full consideration of differential and linear cryptanalysis security. In this paper, we investigate the impossible differential properties of New-structure series, and we show that there always exists 14/∞/19/15 rounds impossible differential for New-structure Ⅰ, Ⅱ, Ⅲ and Ⅳ respectively.