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

• Published in: Advances in Information and Computer Security Vol. 11689; pp. 129 - 145
• Main Authors: Sakamoto, Kosei, Minematsu, Kazuhiko, Shibata, Nao, Shigeri, Maki, Kubo, Hiroyasu, Funabiki, Yuki, Bogdanov, Andrey, Morioka, Sumio, Isobe, Takanori
• Format: Book Chapter
• Language: English
• Published: Switzerland Springer International Publishing AG 2019; Springer International Publishing
• Series: Lecture Notes in Computer Science
• ISBN: 3030268330; 9783030268336
• ISSN: 0302-9743; 1611-3349
• DOI: 10.1007/978-3-030-26834-3_8

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 Tweakable TWINE is quite efficient, has the same number of rounds as TWINE with extremely simple tweak schedule.