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ASIACRYPT
2007
Springer

Generic Attacks on Unbalanced Feistel Schemes with Expanding Functions

11 years 5 months ago
Generic Attacks on Unbalanced Feistel Schemes with Expanding Functions
Unbalanced Feistel schemes with expanding functions are used to construct pseudo-random permutations from kn bits to kn bits by using random functions from n bits to (k − 1)n bits. At each round, all the bits except n bits are changed by using a function that depends only on these n bits. C.S.Jutla [6] investigated such schemes, which he denotes by Fd k , where d is the number of rounds. In this paper, we describe novel Known Plaintext Attacks (KPA) and Non Adaptive Chosen Plaintext Attacks (CPA-1) against these schemes. With these attacks we will often be able to improve the result of C.S.Jutla. We also give precise formulas for the complexity of our attacks in d, k and n. Key words: Unbalanced Feistel permutations, pseudo-random permutations, generic attacks on encryption schemes, Block ciphers.
Jacques Patarin, Valérie Nachef, Côme
Added 07 Jun 2010
Updated 07 Jun 2010
Type Conference
Year 2007
Where ASIACRYPT
Authors Jacques Patarin, Valérie Nachef, Côme Berbain
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