Cryptology ePrint Archive: Report 2017/278

New Observations on Invariant Subspace Attack

Yunwen Liu and Vincent Rijmen

Abstract: Invariant subspace attack is a novel cryptanalytic technique which breaks several recently proposed lightweight block ciphers. In this paper, we propose a new method to bound the dimension of some invariant subspaces in a class of lightweight block ciphers which have a similar structure as the AES but with 4-bit Sboxes. With assumptions on the diffusion layer, the dimension of any invariant subspaces is at most 32 when the inputs into each Sboxes are linearly independent. The observation brings new insights about the invariant subspace attack, as well as lightweight countermeasures to enhance the resistance against it.

Category / Keywords: secret-key cryptography / Invariant subspace attack, AES-like, Lightweight block ciphers

Date: received 27 Mar 2017

Contact author: yunwen liu at esat kuleuven be

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Version: 20170327:102419 (All versions of this report)

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