A practical attack on KeeLoq

Sebastiaan Indesteege, Nathan Keller, Orr Dunkelman, Eli Biham, Bart Preneel

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

KeeLoq is a lightweight block cipher with a 32-bit block size and a 64-bit key. Despite its short key size, it is widely used in remote keyless entry systems and other wireless authentication applications. For example, authentication protocols based on KeeLoq are supposedly used by various car manufacturers in anti-theft mechanisms. This paper presents a practical key recovery attack against KeeLoq that requires 216 known plaintexts and has a time complexity of 244.5 KeeLoq encryptions. It is based on the slide attack and a novel approach to meet-in-the-middle attacks. The fully implemented attack requires 65 minutes to obtain the required data and 7.8 days of calculations on 64 CPU cores. A variant which requires 216 chosen plaintexts needs only 3.4 days on 64 CPU cores. Using only 10 000 euro, an attacker can purchase a cluster of 50 dual core computers that will find the secret key in about two days. We investigated the way KeeLoq is intended to be used in practice and conclude that our attack can be used to subvert the security of real systems. An attacker can acquire chosen plaintexts in practice, and one of the two suggested key derivation schemes for KeeLoq allows to recover the master secret from a single key.

Original languageEnglish
Title of host publicationAdvances in Cryptology - EUROCRYPT 2008 - 27th Annual International Conference on the Theory and Applications of Cryptographic Techniques, Proceedings
Pages1-18
Number of pages18
DOIs
StatePublished - 2008
Externally publishedYes
Event27th Annual International Conference on the Theory and Applications of Cryptographic Techniques, EUROCRYPT 2008 - Istanbul, Turkey
Duration: 13 Apr 200817 Apr 2008

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume4965 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349

Conference

Conference27th Annual International Conference on the Theory and Applications of Cryptographic Techniques, EUROCRYPT 2008
Country/TerritoryTurkey
CityIstanbul
Period13/04/0817/04/08

Bibliographical note

Funding Information:
This work was supported in part by the Concerted Research Action (GOA) Ambiorics 2005/11 of the Flemish Government, by the IAP Programme P6/26 BCRYPT of the Belgian State (Belgian Science Policy), and in part by the European Commission through the IST Programme under Contract IST-2002-507932 ECRYPT.

Keywords

  • Block ciphers
  • Cryptanalysis
  • KeeLoq
  • Meet-in-the-middle attacks
  • Slide attacks

ASJC Scopus subject areas

  • Theoretical Computer Science
  • Computer Science (all)

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