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Communication Dans Un Congrès Année : 2023

Cryptanalysis of Symmetric Primitives over Rings and a Key Recovery Attack on Rubato

Résumé

Symmetric primitives are a cornerstone of cryptography, and have traditionally been defined over fields, where cryptanalysis is now well understood. However, a few symmetric primitives defined over rings Zq for a composite number q have recently been proposed, a setting where security is much less studied. In this paper we focus on studying established algebraic attacks typically defined over fields and the extent of their applicability to symmetric primitives defined over the ring of integers modulo a composite q Based on our analysis, we present an attack on full Rubato, a family of symmetric ciphers proposed by Ha et al. at Eurocrypt 2022 designed to be used in a transciphering framework for approximate fully homomorphic encryption. We show that at least 25 % of the possible choices for q satisfy certain conditions that lead to a successful key recovery attack with complexity significantly lower than the claimed security level for five of the six ciphers in the Rubato family.
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Dates et versions

hal-04282311 , version 1 (13-11-2023)

Identifiants

Citer

Lorenzo Grassi, Irati Manterola Ayala, Martha Norberg Hovd, Morten Øygarden, Håvard Raddum, et al.. Cryptanalysis of Symmetric Primitives over Rings and a Key Recovery Attack on Rubato. Advances in Cryptology - CRYPTO 2023, IACR, Aug 2023, Santa Barbara, United States. pp.305-339, ⟨10.1007/978-3-031-38548-3_11⟩. ⟨hal-04282311⟩
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