Improved Linear Approximations to ARX Ciphers and Attacks Against ChaCha

Murilo Coutinho; T.  C.  Souza Neto

Paper 2021/224

Improved Linear Approximations to ARX Ciphers and Attacks Against ChaCha

Murilo Coutinho and 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.

Metadata

Available format(s): PDF
Category: Secret-key cryptography
Publication info: Published by the IACR in EUROCRYPT 2021
Contact author(s): murilo coutinho @ redes unb br
History: 2021-09-22: revised; 2021-03-02: received; See all versions
Short URL: https://ia.cr/2021/224
License: CC BY

BibTeX

@misc{cryptoeprint:2021/224,
      author = {Murilo Coutinho and T.  C.  Souza Neto},
      title = {Improved Linear Approximations to {ARX} Ciphers and Attacks Against {ChaCha}},
      howpublished = {Cryptology {ePrint} Archive, Paper 2021/224},
      year = {2021},
      url = {https://eprint.iacr.org/2021/224}
}