New Directions in Cryptanalysis of Self-Synchronizing Stream Ciphers

In cryptology we commonly face the problem of finding an unknown key K from the output of an easily computable keyed function F(C, K) where the attacker has the power to choose the public variable C. In this work we focus on self-synchronizing stream ciphers. First we show how to model these primitives in the above-mentioned general problem by relating appropriate functions F to the underlying ciphers. Then we apply the recently proposed framework presented at AfricaCrypt'08 by Fischer et. al. for dealing with this kind of problems to the proposed T-function based self-synchronizing stream cipher by Klimov and Shamir at FSE'05 and show how to deduce some non-trivial information about the key. We also open a new window for answering a crucial question raised by Fischer et. al. regarding the problem of finding weak IV bits which is essential for their attack.

Published in:
Progress In Cryptology - Indocrypt 2008, 5365, 15-26
Presented at:
9th Annual International Conference on Cryptology in India, Kharagpur, INDIA, Dec 14-17, 2008
Springer-Verlag New York, Ms Ingrid Cunningham, 175 Fifth Ave, New York, Ny 10010 Usa

 Record created 2010-11-30, last modified 2018-01-28

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