Further Improving Differential-Linear Attacks: Applications to Chaskey and Serpent
Marek Broll, Federico Canale, Nicolas David, Antonio Flórez-Gutiérrez, Gregor Leander, María Naya‐Plasencia, Yosuke Todo · HAL (Le Centre pour la Communication Scientifique Directe) · 2021
Differential-linear attacks are a cryptanalysis family that has recently benefited from various technical improvements, mainly in the context of ARX constructions. In this paper we push further this refinement, proposing several new improvements. In particular, we develop a better understanding of the related correlations, improve upon the statistics by using the LLR, and finally use ideas from conditional differentials for finding many right pairs. We illustrate the usefulness of these ideas by presenting the first 7.5-round attack on Chaskey. Finally, we present a new competitive attack on 12 rounds of Serpent, and as such the first cryptanalytic progress on Serpent in 10 years.