Tweakable TWINE: Building a Tweakable Block Cipher on Generalized Feistel Structure

Kosei SAKAMOTO; Kazuhiko MINEMATSU; Nao SHIBATA; Maki SHIGERI; Hiroyasu KUBO; Yuki FUNABIKI; Andrey BOGDANOV; Sumio MORIOKA; Takanori ISOBE

doi:10.1587/transfun.2019EAP1141

Regular Section

Tweakable TWINE: Building a Tweakable Block Cipher on Generalized Feistel Structure

Kosei SAKAMOTO, Kazuhiko MINEMATSU, Nao SHIBATA, Maki SHIGERI, Hiroyasu KUBO, Yuki FUNABIKI, Andrey BOGDANOV, Sumio MORIOKA, Takanori ISOBE

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Keywords: twekakble block cipher, generalized feistel structure, TWINE, MILP

JOURNAL RESTRICTED ACCESS

2020 Volume E103.A Issue 12 Pages 1629-1639

DOI https://doi.org/10.1587/transfun.2019EAP1141

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Abstract

Tweakable block cipher (TBC) is an extension of conventional block cipher. We study how to build a TBC based on generalized Feistel structure (GFS), a classical block cipher construction. While known dedicated TBC proposals are based on substitution-permutation network (SPN), GFS has not been used for building TBC. In particular, we take 64-bit GFS block cipher TWINE and try to make it tweakable with a minimum change. To find a best one from a large number of candidates, we performed a comprehensive search with a help of mixed integer linear programming (MILP) solver. As a result, our proposal TWINE is quite efficient, has the same number of rounds as TWINE with extremely simple tweak schedule.

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