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Communication Dans Un Congrès Année : 2022

Practical homomorphic evaluation of block-cipher-based hash functions with applications

Résumé

Fully homomorphic encryption (FHE) is a powerful cryptographic technique allowing to perform computation directly over encrypted data. Motivated by the overhead induced by the homomorphic ciphertexts during encryption and transmission, the transciphering technique, consisting in switching from a symmetric encryption to FHE encrypted data was investigated in several papers. Different stream and block ciphers were evaluated in terms of their "FHE-friendliness", meaning practical implementations costs while maintaining sufficient security levels. In this work, we present a first evaluation of hash functions in the homomorphic domain, based on well-chosen block ciphers. More precisely, we investigate the cost of transforming PRINCE and SIMON, two lightweight block-ciphers into secure hash functions using well-established block-cipher-based hash functions constructions, and provide evaluation under bootstrappable FHE schemes. We also motivate the necessity of practical homomorphic evaluation of hash functions by providing several use cases in which the integrity of private data is also required. In particular, our hash constructions can be of significant use in a threshold-homomorphic based protocol for the single secret leader election problem occuring in blockchains with Proof-of-stake consensus. Our experiments showed that using a TFHE implementation of a hash function, we are able to achieve practical runtime, and appropriate security levels.
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Dates et versions

cea-04463301 , version 1 (16-02-2024)

Identifiants

Citer

Adda-Akram Bendoukha, Oana Stan, Renaud Sirdey, Nicolas Quero, Luciano Freitas. Practical homomorphic evaluation of block-cipher-based hash functions with applications. 15th International Symposium on Foundations & Practice of Security, Dec 2022, Ottawa, Canada. pp.88-103, ⟨10.1007/978-3-031-30122-3_6⟩. ⟨cea-04463301⟩
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