[Resource Topic] 2022/243: A Greater GIFT: Strengthening GIFT against Statistical Cryptanalysis

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A Greater GIFT: Strengthening GIFT against Statistical Cryptanalysis

Authors: Ling Sun, Bart Preneel, Wei Wang, Meiqin Wang


GIFT-64 is a 64-bit block cipher with a 128-bit key that is more lightweight than PRESENT. This paper provides a detailed analysis of GIFT-64 against differential and linear attacks. Our work complements automatic search methods for the best differential and linear characteristics with a careful manual analysis. This hybrid approach leads to new insights. In the differential setting, we theoretically explain the existence of differential characteristics with two active S-boxes per round and derive some novel properties of these characteristics. Furthermore, we prove that all optimal differential characteristics of GIFT-64 covering more than seven rounds must activate two S-boxes per round. We can construct all optimal characteristics by hand. In parallel to the work in the differential setting, we conduct a similar analysis in the linear setting. However, unlike the clear view in differential setting, the optimal linear characteristics of GIFT-64 must have at least one round activating only one S-box. Moreover, with the assistance of automatic searching methods, we identify 24 GIFT-64 variants achieving better resistance against differential attack while maintaining a similar security level against a linear attack. Since the new variants strengthen GIFT-64 against statistical cryptanalysis, we claim that the number of rounds could be reduced from 28 to 26 for the variants. This observation enables us to create a cipher with lower energy consumption than GIFT-64. Similarly to the case in GIFT-64, we do not claim any related-key security for the round-reduced variant as this is not relevant for most applications.

ePrint: https://eprint.iacr.org/2022/243

Talk: https://www.youtube.com/watch?v=dnKd7BCABIw

Slides: https://iacr.org/submit/files/slides/2022/eurocrypt/eurocrypt2022/362/slides.pdf

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