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733 results

    • Seminar

    • Cryptography

    Discrete logarithm computation in finite fields GF(p^k) with NFS

    • March 01, 2019

    • IRMAR - Université de Rennes - Campus Beaulieu Bat. 22, RDC, Rennes - Amphi Lebesgue

    Speaker : Aurore Guillevic - INRIA

    Pairings on elliptic curves are involved in signatures, NIZK, and recently in blockchains (ZK-SNARKS).<br/> These pairings take as input two points on an elliptic curve E over a finite field, and output a value in an extension of that finite field. Usually for efficiency reasons, this extension degree is a power of 2 and 3 (such as 12,18,24), and moreover the characteristic of the finite field has[…]
    • Seminar

    • Cryptography

    Post-quantum cryptography based on supersingular isogeny problems?

    • October 25, 2019

    • IRMAR - Université de Rennes - Campus Beaulieu Bat. 22, RDC, Rennes - Amphi Lebesgue

    Speaker : Christophe Petit - University of Birmingham

    The security of many cryptographic protocols in use today relies on the computational hardness of mathematical problems such as integer factorization. These problems can be solved using quantum computers, and therefore most of our security infrastructures will become completely insecure once quantum computers are built. Post-quantum cryptography aims at developing security protocols that will[…]
    • Seminar

    • Cryptography

    Improving greedy nonrandomness detectors for stream ciphers

    • March 24, 2017

    • IRMAR - Université de Rennes - Campus Beaulieu Bat. 22, RDC, Rennes - Amphi Lebesgue

    Speaker : Paul Stankovski - Université de Lund

    We consider the problem of designing distinguishers and nonrandomness detectors for stream ciphers using the maximum degree monomial test. We construct an improved algorithm to determine the subset of key and IV-bits used in the test. The algorithm is generic, and can be applied to any stream cipher. In addition to this, the algorithm is highly tweakable, and can be adapted depending on the[…]
    • Seminar

    • Cryptography

    Towards the Implementation of Efficient and Distributable Pairing-based Crypto Library

    • December 01, 2017

    • IRMAR - Université de Rennes - Campus Beaulieu Bat. 22, RDC, Rennes - Amphi Lebesgue

    Speaker : Al-Amin Khandaker - Okayama University

    Pairing-based cryptography is popular among the cryptographic protocol researchers for its eccentric provable security. Protocol side researchers often see pairing as a black box. They often need to test the correctness of their proposal. Typically, mathematicians and cryptography engineers try to make the underlying operations of pairing-based crypto efficient. In addition, different types of[…]
    • Seminar

    • Cryptography

    Encryption Switching Protocols

    • November 25, 2016

    • IRMAR - Université de Rennes - Campus Beaulieu Bat. 22, RDC, Rennes - Amphi Lebesgue

    Speaker : Geoffroy Couteau - ENS

    (Joint work with Thomas Peters, and David Pointcheval) We put forth a novel cryptographic primitive: encryption switching protocol (ESP), allowing to switch between two encryption schemes. Intuitively, this two-party protocol converts given ciphertexts from one scheme into ciphertexts of the same messages in the other scheme, for any polynomial number of switches, in any direction. Although ESP is[…]
    • Seminar

    • Cryptography

    Adaptive Oblivious Transfer with Access Control for NC1 from LWE

    • June 16, 2017

    • IRMAR - Université de Rennes - Campus Beaulieu Bat. 22, RDC, Rennes - Amphi Lebesgue

    Speaker : Fabrice Mouhartem - Ens Lyon

    Adaptive oblivious transfer (OT) is a protocol where a sender initially commits to a database M_1, …, M_N. Then, a receiver can query the sender up to k times with private indexes ρ_1, …, ρ_k so as to obtain M_{ρ_1}, …, M_{ρ_k} and nothing else. Moreover, for each i ∈ [k], the receiver’s choice ρ_i may depend on previously obtained messages {M_{ρ_j}}_{j< i} . Oblivious transfer with access control[…]