Equivalence of Generalised Feistel Networks

This paper focuses on equivalences between Generalised Feistel Networks (GFN) of type-II. We introduce a new definition of equivalence which captures the concept that two GFNs are identical up to re-labelling of the inputs/outputs, and give a procedure to test this equivalence relation. Such two GFN...

Full description

Saved in:
Bibliographic Details
Published inIACR Transactions on Symmetric Cryptology Vol. 2024; no. 1; pp. 412 - 440
Main Authors Derbez, Patrick, Euler, Marie
Format Journal Article
LanguageEnglish
Published Ruhr Universität Bochum 01.03.2024
Ruhr-Universität Bochum
Subjects
Computer Science
Cryptography and Security
GFN
LBlock
TWINE
WARP
WARP
LBlock
TWINE
GFN
Online AccessGet full text

Cover

More Information
Summary:This paper focuses on equivalences between Generalised Feistel Networks (GFN) of type-II. We introduce a new definition of equivalence which captures the concept that two GFNs are identical up to re-labelling of the inputs/outputs, and give a procedure to test this equivalence relation. Such two GFNs are therefore cryptographically equivalent for several classes of attacks. It induces a reduction o the space of possible GFNs: the set of the (k!)2 possible even-odd GFNs with 2k branches can be partitioned into k! different classes.This result can be very useful when looking for an optimal GFN regarding specific computationally intensive properties, such as the minimal number of active S-boxes in a differential trail. We also show that in several previous papers, many GFN candidates are redundant as they belong to only a few classes. Because of this reduction of candidates, we are also able to suggest better permutations than the one of WARP: they reach 64 active S-boxes in one round less and still have the same diffusion round that WARP. Finally, we also point out a new family of permutations with good diffusion properties.
ISSN:2519-173X
2519-173X
DOI:10.46586/tosc.v2024.i1.412-440