International Association for Cryptologic Research

International Association
for Cryptologic Research


Pitfalls and Shortcomings for Decompositions and Alignment

Baptiste Lambin , Univeristy of Luxembourg
Gregor Leander , Ruhr-Universit├Ąt Bochum
Patrick Neumann , Ruhr-Universit├Ąt Bochum
DOI: 10.1007/978-3-031-30634-1_11 (login may be required)
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Presentation: Slides
Conference: EUROCRYPT 2023
Abstract: In this paper we, for the first time, study the question under which circumstances decomposing a round function of a Substitution-Permutation Network is possible uniquely. More precisely, we provide necessary and sufficient criteria for the non-linear layer on when a decomposition is unique. Our results in particular imply that, when cryptographically strong S-boxes are used, the decomposition is indeed unique. We then apply our findings to the notion of alignment, pointing out that the previous definition allows for primitives that are both aligned and unaligned simultaneously. As a second result, we present experimental data that shows that alignment might only have limited impact. For this, we compare aligned and unaligned versions of the cipher PRESENT.
  title={Pitfalls and Shortcomings for Decompositions and Alignment},
  author={Baptiste Lambin and Gregor Leander and Patrick Neumann},