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Towards Tight Security of Cascaded LRW2
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| Conference: | TCC 2018 |
| Abstract: | The Cascaded LRW2 tweakable block cipher was introduced by Landecker et al. at CRYPTO 2012, and proven secure up to $$2^{2n/3}$$ queries. There has not been any attack on the construction faster than the generic attack in $$2^n$$ queries. In this work we initiate the quest towards a tight bound. We first present a distinguishing attack in $$2n^{1/2}2^{3n/4}$$ queries against a generalized version of the scheme. The attack is supported with an experimental verification and a formal success probability analysis. We subsequently discuss non-trivial bottlenecks in proving tight security, most importantly the distinguisher’s freedom in choosing the tweak values. Finally, we prove that if every tweak value occurs at most $$2^{n/4}$$ times, Cascaded LRW2 is secure up to $$2^{3n/4}$$ queries. |
BibTeX
@inproceedings{tcc-2018-29034,
title={Towards Tight Security of Cascaded LRW2},
booktitle={Theory of Cryptography},
series={Theory of Cryptography},
publisher={Springer},
volume={11240},
pages={192-222},
doi={10.1007/978-3-030-03810-6_8},
author={Bart Mennink},
year=2018
}