Description
We consider a generalisation of the encryption from "one-to-one'' to "one-to-many'' communication, i.e. broadcast encryption. The objective is to allow a center to send secret messages to a large number of receivers. The security notion in “one-to-many” communications needs to be extended beyond the notion of confidentiality in “one-to-one” encryption in order to meet practical requirements. Two main functionalities are studied: (1) traitor tracing which identifies the malicious users who leak their secrets to a pirate and (2) revocation which prevents malicious users and/or non-legitimate ones from decrypting broadcasted information.<br/> In the first part of the talk, we focus on combinatorial schemes. We consider the Exclusive Set System (ESS) which has been originally designed to support revocation. We propose a method to integrate the black-box tracing capacity in ESS by introducing a technique called "shadow group testing''.<br/> The second part of the talk discusses the techniques for constructing algebraic schemes which can overcome some limitations of combinatorial schemes. We propose a lattice-based traitor tracing of which the security is based on the hardness of a new variant of the Learning With Errors problem, namely k-LWE (for k traitors). We then prove the hardness of the k-LWE problem which implies that the proposed traitor tracing scheme is asymptotically as efficient as the Regev LWE-based encryption. Our technique can also be used to improve the Boneh-Freeman reduction from SIS to k-SIS from exponential loss to polynomial loss in k (thus answer their open problem of a tighter reduction from SIS to k-SIS). We finally consider the combination of algebraic and combinatorial methods and discuss some promising directions.
Next sessions
-
On the average hardness of SIVP for module lattices of fixed rank
Speaker : 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
Speaker : 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
-
-
Lightweight (AND, XOR) Implementations of Large-Degree S-boxes
Speaker : 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
-
Symmetrical primitive
-
Implementation of cryptographic algorithm
-
-
Algorithms for post-quantum commutative group actions
Speaker : 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
Speaker : 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
-