Description
In November 2004, the European Network of Excellence for Cryptology (ECRYPT) launched a call for new stream cipher primitives. Authors from academia as well as industry submitted 34 designs, and in May 2008, 8 ciphers were chosen for the eSTREAM final portfolio. In this talk, we look back at the history of stream ciphers to understand the design choices made by cryptographers today. We start by reviewing "historical" designs based on linear feedback shift registers, such as the GSM A5/1 cipher. We explain basic cryptanalytic techniques - such as guess-and-determine attacks and correlation attacks - used to break LFSR-based ciphers. We also stop briefly to examine the importance of state size and key/IV length w.r.t. time-memory trade-offs. We then move on to the beginning of 2000s, which brought us new designs from the NESSIE research project, including SNOW 2.0, later to become the 3G mobile standard SNOW 3G. We discuss how new cryptanalytic tools, most notably algebraic cryptanalysis, reshaped design principles in modern ciphers, and review some of the eSTREAM submissions.<br/> In the second part of this talk, we focus on the cryptanalysis of one of the eSTREAM finalists, Moustique. We give a step-by-step overview of our attack that allows to recover the full 96-bit key in 2^{38} steps, using related keys, and allows to speed up exhaustive search in the standard case (without related keys) by a factor 28. Here, we invite the audience to interact, identify weaknesses that lead to the break and propose tweaks to thwart the attack. Cryptanalysis of Moustique is joint work with Vincent Rijmen, Tor E. Bjorstad, Christian Rechberger, Matt Robshaw and Gautham Sekar.
Prochains exposés
-
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
-
TRNG
-
-
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
-