Security Analysis of Key-Alternating Feistel Ciphers

Rodolphe Lampe; Yannick Seurin

Paper 2014/151

Security Analysis of Key-Alternating Feistel Ciphers

Rodolphe Lampe and Yannick Seurin

Abstract

We study the security of \emph{key-alternating Feistel} ciphers, a class of key-alternating ciphers with a Feistel structure. Alternatively, this may be viewed as the study of Feistel ciphers where the pseudorandom round functions are of the form $F_{i} (x \oplus k_{i})$ , where $k_{i}$ is the (secret) round key and $F_{i}$ is a \emph{public} random function that the adversary is allowed to query in a black-box way. Interestingly, our results can be seen as a generalization of traditional results \emph{à la} Luby-Rackoff in the sense that we can derive results for this model by simply letting the number of queries of the adversary to the public random functions $F_{i}$ be zero in our general bounds. We make an extensive use of the coupling technique. In particular (and as a result of independent interest), we improve the analysis of the coupling probability for balanced Feistel schemes previously carried out by Hoang and Rogaway (CRYPTO 2010).

Note: An abridged version appears in the proceedings of FSE 2014. This is the full version.

Metadata

Available format(s): PDF
Category: Secret-key cryptography
Publication info: A minor revision of an IACR publication in FSE 2014
Keywords: block cipher key-alternating cipher Feistel cipher coupling provable security
Contact author(s): rodolphe lampe @ gmail com
yannick seurin @ m4x org
History: 2014-03-01: received
Short URL: https://ia.cr/2014/151
License: CC BY

BibTeX

@misc{cryptoeprint:2014/151,
      author = {Rodolphe Lampe and Yannick Seurin},
      title = {Security Analysis of Key-Alternating Feistel Ciphers},
      howpublished = {Cryptology {ePrint} Archive, Paper 2014/151},
      year = {2014},
      url = {https://eprint.iacr.org/2014/151}
}