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

Authors:
Murilo Coutinho Silva , CEPESC
Tertuliano C. de Souza Neto , CEPESC
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DOI: 10.1007/978-3-030-77870-5_25 (login may be required)
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Conference: EUROCRYPT 2021
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.
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BibTeX
@inproceedings{eurocrypt-2021-30810,
  title={Improved Linear Approximations to ARX Ciphers and Attacks Against ChaCha},
  publisher={Springer-Verlag},
  doi={10.1007/978-3-030-77870-5_25},
  author={Murilo Coutinho Silva and Tertuliano C. de Souza Neto},
  year=2021
}