Journal of Cryptology

, Volume 18, Issue 4, pp 291–311 | Cite as

Cryptanalysis of Skipjack Reduced to 31 Rounds Using Impossible Differentials

  • Eli Biham
  • Alex Biryukov
  • Adi Shamir


In this paper we present a cryptanalytic technique, based on impossible differentials. We use it to show that recovering keys of Skipjack reduced from 32 to 31 rounds can be performed faster than exhaustive search. We also describe the Yoyo game (a tool that can be used against reduced-round Skipjack), and other properties of Skipjack.

Skipjack Cryptanalysis Differential cryptanalysis Impossible differentials Yoyo game Adaptive attacks 


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Copyright information

© Springer 2005

Authors and Affiliations

  1. 1.Computer Science Department, Technion – Israel Institute of Technology, Haifa 32000Israel
  2. 2.Dept. ESAT/SCD-COSIC, Katholieke Universiteit Leuven, Kasteelpark Arenberg 10, B-3001 Leuven-HeverleeBelgium
  3. 3.Department of Applied Mathematics and Computer Science, Weizmann Institute of Science, Rehovot 76100Israel

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