Description
Un compromis temps-mémoire cryptanalytique est une technique qui vise à réduire le temps nécessaire pour effectuer certaines attaques cryptographiques telles que l’inversion d’une fonction à sens unique. Une telle inversion intervient dans une des principales applications des compromis temps-mémoire : le cassage de mots de passe. La technique requiert un très lourd pré-calcul qui génère des tables utilisables pour accélérer la recherche exhaustive de l’attaque. L ’attaque par compromis temps-mémoire est d’autant plus rapide qu’il y a de mémoire allouée à l’algorithme. Cependant, en pratique, la mémoire est souvent un facteur limitant. Nous évaluons l’impact d’un problème nécessitant une grande mémoire sur la technique des compromis temps-mémoire, notamment en se plaçant dans le contexte où une mémoire externe lente est utilisée à la place d’une mémoire rapide limitée (RAM). Nous établissons qu’une telle approche est applicable dans des cas pratiques, qui sont identifiés. Nous proposons ensuite une nouvelle construction de compromis temps-mémoire qui repose sur des fonctions de hachage minimales parfaites, et dont le stockage est moindre que sur les techniques de compression de tables existantes. Finalement, nous proposons une comparaison entre les améliorations existantes, possiblement combinées, et notre nouvelle technique.<br/> lien: rien
Prochains exposés
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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[…] -
Attacks and Remedies for Randomness in AI: Cryptanalysis of PHILOX and THREEFRY
Orateur : Yevhen Perehuda - Ruhr-University Bochum
In this work, we address the critical yet understudied question of the security of the most widely deployed pseudorandom number generators (PRNGs) in AI applications. We show that these generators are vulnerable to practical and low-cost attacks. With this in mind, we conduct an extensive survey of randomness usage in current applications to understand the efficiency requirements imposed in[…]-
Cryptography
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Lightweight (AND, XOR) Implementations of Large-Degree S-boxes
Orateur : Marie Bolzer - LORIA
The problem of finding a minimal circuit to implement a given function is one of the oldest in electronics. In cryptography, the focus is on small functions, especially on S-boxes which are classically the only non-linear functions in iterated block ciphers. In this work, we propose new ad-hoc automatic tools to look for lightweight implementations of non-linear functions on up to 5 variables for[…]-
Cryptography
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Symmetrical primitive
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Implementation of cryptographic algorithm
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Algorithms for post-quantum commutative group actions
Orateur : Marc Houben - Inria Bordeaux
At the historical foundation of isogeny-based cryptography lies a scheme known as CRS; a key exchange protocol based on class group actions on elliptic curves. Along with more efficient variants, such as CSIDH, this framework has emerged as a powerful building block for the construction of advanced post-quantum cryptographic primitives. Unfortunately, all protocols in this line of work are[…] -
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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