Paper 2006/250 Original: eprint.iacr.org/2006/250 ↗
Linear Cryptanalysis of CTC
Abstract
CTC is a toy cipher designed by Courtois in order to prove the strength of algebraic attacks. In this paper we study the differential and the linear behavior of the 85 S-boxes version, which is attacked using algebraic techniques faster than exhaustive key search. We show that an $n$-round variant of the cipher can be attacked by a linear attack using only $2^{2n+2}$ known plaintexts, with a negligible time complexity. We conclude that CTC is insecure, even for quite a large number of rounds. We note that our observations can be probably used to devise other attacks that exploit the relatively slow diffusion of CTC.
Metadata
- Available format(s)
PDF- Category
- Secret-key cryptography
- Publication info
- Preprint.
- History
- 2006-07-24: last updated
- 2006-07-24: published
- Short URL
- https://ia.cr/2006/250
- License
- https://creativecommons.org/licenses/by/4.0/
BibTeX
@misc{cryptoeprint:2006/250,
author = {Orr Dunkelman and Nathan Keller},
title = {Linear Cryptanalysis of CTC},
howpublished = {Cryptology {ePrint} Archive, Paper 2006/250},
year = {2006},
url = {https://eprint.iacr.org/2006/250}
}