Description
Authentication protocols, run between a prover and a verifier, allow the verifier to check the legitimacy of the prover. A legitimate prover should always authenticate (the correctness requirement), while illegitimate parties (adversaries) should not authenticate (the soundness or impersonation resistance requirement). Secure authentication protocols thwart most Man-in-the-Middle (MIM) attacks, such as replays, but they do not prevent relay attacks , where a coalition of two adversaries, a leech and a ghost , forwards messages between an honest verifier and an honest, far-away prover so as to let the illegitimate ghost authenticate.<br/> Distance-bounding protocols strengthen the security of authentication so as to prevent pure relaying, by enabling the verifier to upper-bound his distance to the prover. This is done by adding a number of time-critical challenge-response rounds, where bits are exchanged over a fast channel; the verifier measures the challenge-response roundtrip and compares it to a time-based proximity bound. There are four attacks such protocols should prevent: mafia fraud, where a MIM adversary tries to authenticate in the presence of a far-away (honest) prover, without purely relaying messages (the clock prevents this); terrorist fraud, where the prover is dishonest and helps the MIM adversary authenticate insofar as this help does not give the adversary any advantage for future (unaided) authentication; distance fraud, where a far-away prover wants to prove he is within the verifier's proximity; and (lazy-round) impersonation security, requiring a degree of impersonation security even for the exchanges that are not timed. Constructing distance-bounding protocols is a highly non-trivial task, since often providing security against one requirement creates a vulnerability with respect to a different requirement. I propose to describe how to construct distance-bounding protocols which are probably secure and also guarantee the prover's privacy.
Prochains exposés
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Attacking the Supersingular Isogeny Problem: From the Delfs–Galbraith algorithm to oriented graphs
Orateur : Arthur Herlédan Le Merdy - COSIC, KU Leuven
The threat of quantum computers motivates the introduction of new hard problems for cryptography.One promising candidate is the Isogeny problem: given two elliptic curves, compute a “nice’’ map between them, called an isogeny.In this talk, we study classical attacks on this problem, specialised to supersingular elliptic curves, on which the security of current isogeny-based cryptography relies. In[…]-
Cryptography
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Verification of Rust Cryptographic Implementations with Aeneas
Orateur : Aymeric Fromherz - Inria
From secure communications to online banking, cryptography is the cornerstone of most modern secure applications. Unfortunately, cryptographic design and implementation is notoriously error-prone, with a long history of design flaws, implementation bugs, and high-profile attacks. To address this issue, several projects proposed the use of formal verification techniques to statically ensure the[…] -
On the average hardness of SIVP for module lattices of fixed rank
Orateur : Radu Toma - Sorbonne Université
In joint work with Koen de Boer, Aurel Page, and Benjamin Wesolowski, we study the hardness of the approximate Shortest Independent Vectors Problem (SIVP) for random module lattices. We use here a natural notion of randomness as defined originally by Siegel through Haar measures. By proving a reduction, we show it is essentially as hard as the problem for arbitrary instances. While this was[…] -
Endomorphisms via Splittings
Orateur : Min-Yi Shen - No Affiliation
One of the fundamental hardness assumptions underlying isogeny-based cryptography is the problem of finding a non-trivial endomorphism of a given supersingular elliptic curve. In this talk, we show that the problem is related to the problem of finding a splitting of a principally polarised superspecial abelian surface. In particular, we provide formal security reductions and a proof-of-concept[…]-
Cryptography
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