Description
Fully Homomorphic Encryption is a powerful cryptographic construction, enabling to securely compute all functions on encrypted data, and decrypt the result of the function applied on the real data.<br/> This construction allows to securely delegate computation, which is a very important property with the increasing of the Cloud computing. Many client-server applications are appearing, all needing the computation delegating property of FHE, with different notions of security and cost. The client-server frameworks usually considered a client with small storage and computation possibilities and a cloud powerful for both. The client wants to delegate his computation with small computation and communication cost, which directly leads to Symmetric Encryption. As the frameworks considerate two types of encryption, we study the links and differences between them. Efficiency and security are not studied the same way, on one hand a SE scheme is evaluated relatively to its practical speed, storage cost and concrete cryptanalysis. On the other hand FHE is more a theoretic construction, evaluated relatively to its security assumptions and homomorphic capacities. To combine these two approaches, we need to study the different costs and efficiency implications from one type to the other. Our approach is to consider a particular family of FHE and adapt a SE scheme to build a framework efficient relatively to both metrics. Part of the study is to analyze the previous symmetric constructions relatively to this framework, more specifically figure out the error growth implied in the homomorphic decryption of the SE scheme. As minimizing this factor is not linked with SE efficiency, we have to considerate all kinds of SE constructions and find the properties suitable for FHE. First, with block-cipher constructions we can focus on the number of iterations, on the circuit depth and on the chaining mode used. Then stream-cipher constructions allow to study the error growth depending on the number of outputted bits. Finally the existent constructions of both families are not optimized nor totally suitable for our framework, leading us to the next step. This study enables us to compare the different alternatives and to conclude on properties to conserve or discard. We select some properties of known SE schemes behaving well with the FHE scheme consideration and study their compatibilities. Choosing the good characteristics for the SE-FHE framework gives us the starting point for a future optimal design.
Prochains exposés
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La crypto-graphie et les crypto-monnaies
Orateur : Daniel Augot - INRIA Saclay—Île-de-France
De nos jours, la requête «crypto» dans un moteur de recherche renvoieaux cryptomonnaies. Mais «crypto means crypto», et on peut se poser laquestion des liens pertinents entre les deux domaines. D'un coté, le monde des cryptomonnaies et de la technologiesous-jacente s'est développé et évolue encore en dehors du mondeacadémique. Il faut suivre d'un coté des posts de blog, des fils dediscussion X[…] -
SoK: Security of the Ascon Modes
Orateur : Charlotte Lefevre - Radboud University
The Ascon authenticated encryption scheme and hash function of Dobraunig et al (Journal of Cryptology 2021) were recently selected as winner of the NIST lightweight cryptography competition. The mode underlying Ascon authenticated encryption (Ascon-AE) resembles ideas of SpongeWrap, but not quite, and various works have investigated the generic security of Ascon-AE, all covering different attack[…] -
Comprehensive Modelling of Power Noise via Gaussian Processes with Applications to True Random Number Generators
Orateur : Maciej Skorski - Laboratoire Hubert Curien
The talk examines power noise modelling through Gaussian Processes for secure True Random Number Generators. While revisiting one-sided fractional Brownian motion, we obtain novel contributions by quantifying posterior uncertainty in exact analytical form, establishing quasi-stationary properties, and developing rigorous time-frequency analysis. These results are applied to model oscillator[…]-
Cryptography
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TRNG
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CryptoVerif: a computationally-sound security protocol verifier
Orateur : Bruno Blanchet - Inria
CryptoVerif is a security protocol verifier sound in the computational model of cryptography. It produces proofs by sequences of games, like those done manually by cryptographers. It has an automatic proof strategy and can also be guided by the user. It provides a generic method for specifying security assumptions on many cryptographic primitives, and can prove secrecy, authentication, and[…]-
Cryptography
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