Description
Since the 1980s, two approaches have been developed for analyzing security protocols. One of the approaches relies on a computational model that considers issues of complexity and probability. This approach captures a strong notion of security, guaranteed against all probabilistic polynomial-time attacks. The other approach relies on a symbolic model of protocol executions in which cryptographic primitives are treated as black boxes. Since the seminal work of Dolev and Yao, it has been realized that this latter approach enables significantly simpler and often automated proofs. However, the guarantees that it offers have been quite unclear.<br/> We present two results that show soundness of formal models with respect to computational notions of security.<br/> First, we establish that symbolic integrity and secrecy proofs are sound with respect to the computational model in the case of protocols that use signatures and asymmetric encryption. This is a join work with Bogdan Warinschi. Secondly, we study the link between formal and cryptographic models for security protocols in the presence of a passive adversary, for abitrary equational theories. We define a framework for comparing a cryptographic implementation and its idealization w.r.t. various security notions. In particular, we concentrate on the computationnal soundness of static equivalence, a standard tool in cryptographic $\pi$-calculi. This is a join work with Mathieu Baudet and Steve Kremer.
Prochains exposés
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Computational assumptions in the quantum world
Orateur : Alex Bredariol Grilo - LIP6 (CNRS / Sorbonne Université)
QKD is a landmark of how quantum resources allow us to implement cryptographicfunctionalities with a level of security that is not achievable only with classical resources.However, key agreement is not sufficient to implement all functionalities of interest, and it iswell-known that they cannot be implemented with perfect security, even if we have accessto quantum resources. Thus, computational[…]-
Cryptographie
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Polytopes in the Fiat-Shamir with Aborts Paradigm
Orateur : Hugo Beguinet - ENS Paris / Thales
The Fiat-Shamir with Aborts paradigm (FSwA) uses rejection sampling to remove a secret’s dependency on a given source distribution. Recent results revealed that unlike the uniform distribution in the hypercube, both the continuous Gaussian and the uniform distribution within the hypersphere minimise the rejection rate and the size of the proof of knowledge. However, in practice both these[…]-
Cryptographie
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Primitive asymétrique
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Mode et protocole
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Post-quantum Group-based Cryptography
Orateur : Delaram Kahrobaei - The City University of New York