Related-key differential attacks on Cobra-H64 and Cobra-H128

Changhoon Lee, Jongsung Kim, Jaechul Sung, Seokhie Hong, Sangjin Lee, Dukjae Moon

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

15 Scopus citations


Cobra-H64 and Cobra-H128, which use data-dependent permutations as a main cryptographic primitive, are 64-bit and 128-bit iterated block ciphers with 128-bit and 256-bit keys, respectively. Since these ciphers use very simple key scheduling and controlled permutation (CP) for fast hardware encryption, they are suitable for wireless communications networks which require high-speed networks. Actually, these ciphers have better hardware performances than other ciphers used in security layers of wireless protocols (Wap, OMA, UMTS, IEEE 802.11 and so on). In this paper, however, we show that Cobra-H64 and Cobra-H128 are vulnerable to related-key differential attacks. We first describe how to construct full-round related-key differential characteristics of Cobra-H64 and Cobra-H128 with high probabilities and then we exploit them to attack full-round Cobra-H64 with a complexity of 215.5 and Cobra-H128 with a complexity of 244.

Original languageEnglish
Title of host publicationCryptography and Coding - 10th IMA International Conference, Proceedings
PublisherSpringer Verlag
Number of pages19
ISBN (Print)354030276X, 9783540302766
StatePublished - 2005
Event10th IMA International Conference on Cryptography and Coding - Cirencester, United Kingdom
Duration: 19 Dec 200521 Dec 2005

Publication series

NameLecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Volume3796 LNCS
ISSN (Print)0302-9743
ISSN (Electronic)1611-3349


Conference10th IMA International Conference on Cryptography and Coding
Country/TerritoryUnited Kingdom


  • Block Ciphers
  • Cobra-H128
  • Cobra-H64
  • Data-Dependent Permutations
  • Related-Key At-tacks


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