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Contributions à l’analyse de canaux auxiliaires sans connaissance des clairs et chiffrés, et à la recherche de S-boxes compactes

Abstract : Cryptography is widely used nowadays, and side channel attacks are known threats. In order to develop suitable countermeasures, these attacks are constantly studied and improved. This document is part with this approach and studies joint distributions attacks which do not need the plaintext nor the ciphertext, contrary to classical attacks. First, new variants which improve this attack are proposed. They mainly consist in observing more or different intermediate variables, and adapt theoretical distributions accordingly. Then, a practical experiment is done on a microcontroller which validates the attack apart from simulations. Finally, several solutions that compromise masked implementations are proposed. They consist in using the fact that some masks are reused on several internal variables, ending in the quadrivariate attacks proposal. An other main theme about 8 bits S-boxes construction is explored in this document, and originated from the participation to the PACLIDO project which aims to develop a lightweight cryptography algorithm. The S-box is a critical component of cryptographic algorithms and acts to make them resilient to classical cryptanalysis. Unfortunately, this component is often costly in terms of logical gates. We propose two methods for searching compact 8 bit circuits composed of hybrid gates ANDXOR, and show some results close to the literature.
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Léo Reynaud. Contributions à l’analyse de canaux auxiliaires sans connaissance des clairs et chiffrés, et à la recherche de S-boxes compactes. Cryptographie et sécurité [cs.CR]. Université de Limoges, 2019. Français. ⟨NNT : 2019LIMO0107⟩. ⟨tel-02489860⟩

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