Some instant- and practical-time related-key attacks on KTANTAN32/48/64
Författare
Summary, in English
The hardware-attractive block cipher family KTANTAN was studied by Bogdanov and Rechberger who identified flaws in the key schedule and gave a meet-in-the-middle attack. We revisit their result before investigating how to exploit the weakest key bits. We then develop several related-key attacks, e.g., one on KTANTAN32 which finds 28 key bits in time equivalent to $2^{3.0}$ calls to the full KTANTAN32 encryption. The main result is a related-key attack requiring $2^{28.44}$ time (half a minute on a current CPU) to recover the full 80-bit key. For KTANTAN48, we find three key bits in the time of one encryption, and give several other attacks, including full key recovery. For KTANTAN64, the attacks are only slightly more expensive, requiring $2^{10.71}$ time to find 38 key bits, and $2^{32.28}$ for the entire key. For all attacks, the requirements on related-key material are modest as in the forward and backward directions, we only need to flip a single key bit. All attacks succeed with probability one. Our attacks directly contradict the designers' claims. We discuss why this is, and what can be learnt from this.
Publiceringsår
2012
Språk
Engelska
Sidor
213-229
Publikation/Tidskrift/Serie
Lecture Notes in Computer Science
Volym
7118
Fulltext
- Available as PDF - 360 kB
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Dokumenttyp
Del av eller Kapitel i bok
Förlag
Springer
Ämne
- Electrical Engineering, Electronic Engineering, Information Engineering
Nyckelord
- cryptanalysis
- related key
- block cipher
- key schedule
- lightweight cipher
- key-recovery
Conference name
Selected Areas in Cryptography
Conference date
2011-08-10 - 2011-08-12
Conference place
Toronto, Canada
Status
Published
Projekt
- EIT_HSWC:Coding Coding, modulation, security and their implementation
Forskningsgrupp
- Crypto and Security
ISBN/ISSN/Övrigt
- ISSN: 0302-9743
- ISSN: 1611-3349
- ISBN: 978-3-642-28495-3
- ISBN: 978-3-642-28496-0