Abstract
Algebraic attacks have established themselves as a powerful method for the cryptanalysis of LFSR-based keystream generators (e.g., E 0 used in Bluetooth). The attack is based on solving an overdetermined system of low-degree equations R t =0, where R t is an expression in the state of the LFSRs at clock t and one or several successive keystream bits z t ,...,z t + δ .
In fast algebraic attacks, new equations of a lower degree are constructed in a precomputation step. This is done by computing appropriate linear combinations of T successive initial equations R t =0. The successive data complexity of the attack is the number T of successive equations.
We propose a new variant of fast algebraic attacks where the same approach is employed to eliminate some unknowns, making a divide-and-conquer attack possible. In some cases, our variant is applicable whereas the first one is not.
Both variants can have a high successive data complexity (e.g., T≥ 8.822.188 for E 0). We describe how to keep it to a minimum and introduce suitable efficient algorithms for the precomputation step.
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Armknecht, F., Ars, G. (2005). Introducing a New Variant of Fast Algebraic Attacks and Minimizing Their Successive Data Complexity. In: Dawson, E., Vaudenay, S. (eds) Progress in Cryptology – Mycrypt 2005. Mycrypt 2005. Lecture Notes in Computer Science, vol 3715. Springer, Berlin, Heidelberg. https://doi.org/10.1007/11554868_3
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DOI: https://doi.org/10.1007/11554868_3
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