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Concept

Serge Vaudenay

Summary

Serge Vaudenay (born 5 April 1968) is a French cryptographer and professor, director of the Communications Systems Section at the École Polytechnique Fédérale de Lausanne Serge Vaudenay entered the École Normale Supérieure in Paris as a normalien student in 1989. In 1992, he passed the agrégation in mathematics. He completed his Ph.D. studies at the computer science laboratory of École Normale Supérieure, and defended it in 1995 at the Paris Diderot University; his advisor was Jacques Stern. From 1995 to 1999, he was a senior research fellow at French National Centre for Scientific Research (CNRS). In 1999, he moved to a professorship at the École Polytechnique Fédérale de Lausanne where he leads the Laboratory of Security and Cryptography (LASEC). LASEC is host to two popular security programs developed by its members: *iChair, developed by Thomas Baignères and Matthieu Finiasz, a popular on-line submission and review server used by many cryptography conferences; and, *Ophcrack,

Official source

https://en.wikipedia.org/wiki/Serge_Vaudenay

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This course introduces the basics of cryptography. We review several types of cryptographic primitives, when it is safe to use them and how to select the appropriate security parameters. We detail how they work and sketch how they can be implemented.

This course reviews some failure cases in public-key cryptography. It introduces some cryptanalysis techniques. It also presents fundamentals in cryptography such as interactive proofs. Finally, it presents some techniques to validate the security of cryptographic primitives.

This seminar introduces the participants to the current trends, problems, and methods in the area of communication security.

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Related lectures (46)

Related lectures

, ,

Nicolas Anciaux, Xavier Bonnetain, Anne Canteaut, Véronique Cortier, Pierrick Gaudry, Lucca Hirschi, Steve Kremer, Stéphanie Lacour, Gaëtan Leurent, Matthieu Lequesne, Léo Perrin, André Schrottenloher, Emmanuel Thomé, Serge Vaudenay, Christophe Vuillot Dans le but affiché de ralentir la progression de l'épidémie COVID-19, la France envisage de mettre en place un système de traçage des contacts des malades à l'aide d'une application mobile. Les concepteurs de ce type d'applications assurent qu'elles sont respectueuses de la vie privée. Cependant cette notion reste vague. Nous souhaitons donc contribuer au débat public en apportant un éclairage sur ce que pourrait et ne pourrait pas garantir une application de traçage, afin que chacun puisse se forger une opinion sur l'opportunité de son déploiement.

2020

, ,

Iterated attacks are comprised of iterating adversaries who can make

d

plaintext queries, in each iteration to compute a bit, and are trying to distinguish between a random cipher

C

and the ideal random cipher

C^*

based on all bits. In EUROCRYPT '99, Vaudenay showed that a

2d

-decorrelated cipher resists to iterated attacks of order

d

when iterations make almost no common queries. Then, he first asked what the necessary conditions are for a cipher to resist a non-adaptive iterated attack of order

d

. Secondly, he speculated that repeating a plaintext query in different iterations does not provide any advantage to a non-adaptive distinguisher. We close here these two long-standing open problems. We show that, in order to resist non-adaptive iterated attacks of order

d

, decorrelation of order

2d-1

is not sufficient. We do this by providing a counterexample consisting of a cipher decorrelated to the order

2d-1

and a successful non-adaptive iterated attack of order

d

against it. Moreover, we prove that the aforementioned claim is wrong by showing that a higher probability of having a common query between different iterations can translate to a high advantage of the adversary in distinguishing

C

from

C^*

. We provide a counterintuitive example consisting of a cipher decorrelated to the order

2d

which can be broken by an iterated attack of order 1 having a high probability of common queries.

Springer2012

Revisiting Iterated Attacks in the Context of Decorrelation Theory

Asli Bay, Atefeh Mashatan, Serge Vaudenay

Iterated attacks are comprised of iterating adversaries who can make d plaintext queries, in each iteration to compute a bit, and are trying to distinguish between a random cipher C and the perfect cipher C* based on all bits. Vaudenay showed that a 2d-decorrelated cipher resists to iterated attacks of order d. when iterations have almost no common queries. Then, he first asked what the necessary conditions are for a cipher to resist a non-adaptive iterated attack of order d. I.e., whether decorrelation of order 2d-1 could be sufficient. Secondly, he speculated that repeating a plaintext query in different iterations does not provide any advantage to a non-adaptive distinguisher. We close here these two long-standing open problems negatively. For those questions, we provide two counter-intuitive examples. We also deal with adaptive iterated adversaries who can make both plaintext and ciphertext queries in which the future queries are dependent on the past queries. We show that decorrelation of order 2d protects against these attacks of order d. We also study the generalization of these distinguishers for iterations making non-binary outcomes. Finally, we measure the resistance against two well-known statistical distinguishers, namely, differential-linear and boomerang distinguishers and show that 4-decorrelation degree protects against these attacks.

2014

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