[Resource Topic] 2021/224: Improved Linear Approximations to ARX Ciphers and Attacks Against ChaCha

Welcome to the resource topic for 2021/224

Title:
Improved Linear Approximations to ARX Ciphers and Attacks Against ChaCha

Authors: Murilo Coutinho, T. C. Souza Neto

Abstract:

In this paper, we present a new technique which can be used to find better linear approximations in ARX ciphers. Using this technique, we present the first explicitly derived linear approximations for 3 and 4 rounds of ChaCha and, as a consequence, it enables us to improve the recent attacks against ChaCha. Additionally, we present new differentials for 3 and 3.5 rounds of ChaCha that, when combined with the proposed technique, lead to further improvement in the complexity of the Differential-Linear attacks against ChaCha.

ePrint: https://eprint.iacr.org/2021/224

Talk: https://www.youtube.com/watch?v=s_3Dg33crfg

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