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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.
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 exists 14 / ∞ / 19/15 rounds impossible differential for New-structure I, II, III and IV respectively.