Technical Program > Invited Speakers

Implicit Cryptography

Identity-based Communications

Authenticated Key Exchange

Talk Presentation

"HQC and the Future of Code-Based Cryptography: From Foundations to Hybridization"

The approval of HQC (Hamming Quasi-Cyclic) for standardization by NIST marks a major milestone for code-based cryptography in the post-quantum landscape. This talk will first revisit the evolution of code-based encryption, from the seminal McEliece scheme of 1978 to the pioneering work of Alekhnovich, who introduced the a code-based encryption scheme with provable security with proper reduction — set ting the stage for modern constructions. We will then delve into the design of HQC itself, emphasizing its reliance on quasi-cyclic structures and the hardness of decoding random errors, which underpin its secu rity guarantees. Special attention will be given to the HHK transform, a refined framework that ensures an efficient full CCA-2 security (both in the ROM and the QROM), crucial for secure deployment in practice. In the final part of the talk, we will explore cryptographic agility through hybridization strategies, with a focus on a new technique inspired by the X-Wing framework. This approach enables the combination of classical and post-quantum encryption schemes, preserving security guarantees while facilitating a smooth and secure transition to post-quantum infrastructures. The presentation will offer both a historical perspective and a deep dive into the technical and practical innovations that lead to the selection of HQC.

Computer Security

Cryptography

Systems Optimization

Talk Presentation

"Proof of Behavior"

Bitcoin was the beginning of a digital revolution and it is also the birth of the blockchain technology. The security of this technology relies on the concept of Proof of Work (PoW). In order to validate a transaction, a miner needs to produce a PoW. In Bitcoin, a PoW is the computation of an objective of hash, which is find ing a number that satisfies an inequation. Finding this number requires to compute thousands of hash functions. PoW is one of the main negative aspect of this technology since it is highly energy consuming. More over in the case of Bitcoin, the performed hash computations are really useless. Our goal is to design an alternative to PoW, for this purpose we introduce the notion of Proof of Behavior (PoB). Our aim is to change the Proof of Work paradigm. Instead of wasting energy in dummy computations with hash computations, we propose a new approach based on the behavior of the users. We present the notion of PoB, the idea is to incentivize citizens to have responsible behaviors instead of doing useless computations as in PoW. Our idea is to design a mechanism that replaces the Proof of Work and that has a positive impact on the world and a social impact on the behaviors of the citizens. For this, we introduce the notion of Proof of Behavior. We propose a first application to design a new cryptocurrency for the mobility, called EcoMobiCoin for Ecological and Collaborative Mobility Coin. If you can prove that you are biking or walking or using pub lic transportation to go somewhere instead of using your car, or if you can prove that you are using your car with some passengers to go to somewhere, you are generating a Proof of Behavior for eco-responsible mobility and then creating new EcoMobiCoins. This approach aims at facilitating the energy transition that is a key point of the next years.

Fully Homomorphic Encryption

Privacy preserving protocols

Talk Presentation

"Fully homomorphic encryption; what, why, and how?"

This talk is about fully homomorphic encryption (FHE) which enables a computation over encrypted data without decrypting interme diate value. This talk will consist of the past, present, and the future of FHE. I will start with existing FHE schemes, focusing on how they have been developed over a decade. Also, the talk will focus on why it is important, and remaining challenges.