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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Post-Quantum Public-Key Pseudorandom Correlation Functions for OT
Orateur : Mahshid Riahinia - ENS, CNRS
Public-Key Pseudorandom Correlation Functions (PK-PCF) are an exciting recent primitive introduced to enable fast secure computation. Despite significant advances in the group-based setting, success in the post-quantum regime has been much more limited. In this talk, I will introduce an efficient lattice-based PK-PCF for the string OT correlation. At the heart of our result lie several technical[…] -
Predicting Module-Lattice Reduction
Orateur : Paola de Perthuis - CWI
Is module-lattice reduction better than unstructured lattice reduction? This question was highlighted as `Q8' in the Kyber NIST standardization submission (Avanzi et al., 2021), as potentially affecting the concrete security of Kyber and other module-lattice-based schemes. Foundational works on module-lattice reduction (Lee, Pellet-Mary, Stehlé, and Wallet, ASIACRYPT 2019; Mukherjee and Stephens[…]-
Cryptography
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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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