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
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Structured-Seed Local Pseudorandom Generators and their Applications
Speaker : Nikolas Melissaris - IRIF
We introduce structured‑seed local pseudorandom generators (SSL-PRGs), pseudorandom generators whose seed is drawn from an efficiently sampleable, structured distribution rather than uniformly. This seemingly modest relaxation turns out to capture many known applications of local PRGs, yet it can be realized from a broader family of hardness assumptions. Our main technical contribution is a[…]-
Cryptography
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Post-Quantum Public-Key Pseudorandom Correlation Functions for OT
Speaker : 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
Speaker : 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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