Periodic Ciphers with Small Blocks and Cryptanalysis of KeeLoq

Nicolas T. Courtois, Gregory V. Bard, Andrey Bogdanov

    Research output: Chapter in Book/Report/Conference proceedingArticle in proceedingsResearchpeer-review


    KeeLoq is a lightweight block cipher that is massively used in the automobile industry [12, 13, 31, 32]. KeeLoq has two remarkable properties: it is periodic and has a very short block size (32 bits). Many different attacks on KeeLoq have been published in recent years [8, 15, 9, 10, 5]. In this paper we study a unique way of attacking KeeLoq, in which the periodic property of KeeLoq is used in to distinguish 512 rounds of KeeLoq from a random permutation. Our attacks require the knowledge of the entire code-book and are not among the fastest attacks known on this cipher. However one of them works for 100 % of all keys, including so called "strong keys", see [15]. In general, it is important to show how many different attacks are possible on a weak cipher such as KeeLoq.
    Original languageEnglish
    Title of host publicationTatracrypt '07 - 7th Central Europe Conference Of Cryptology
    PublisherSlovak Academy Sciences Mathematical Institute
    Publication date2008
    Publication statusPublished - 2008
    Event7th Central European Conference on Cryptology (TATRACRYPT 2007) - Smolenice, Slovakia
    Duration: 22 Jun 200724 Jun 2007


    Conference7th Central European Conference on Cryptology (TATRACRYPT 2007)
    Internet address
    SeriesTatra Mountains Mathematical Publications


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