I am a cryptography researcher and engineer at CryptoExperts. My main topic of research is Fully Homomorphic Encryption but I have a broader interest in anything cryptography-related and more generally in privacy-preserving technologies and cybersecurity. I am also involved in various projects in CryptoExperts, including development, security audit and consulting.
I (successfully) defended my PhD thesis on 14th of November 2025 at 10:00 am, in Salle des Actes, Ecole normale supérieure, 45 rue d’Ulm, 75005, Paris. You can find the manuscript here and the slides here.
@article{Belaïd_Bon_Rivain_2026,title={Decomposition of Large Look-Up Tables for Fast Homomorphic Evaluation},volume={2026},url={https://eprint.iacr.org/2026/724},abstractnote={ TFHE is one of the most promising scheme in the literature for an adoption of Fully Homomorphic Encryption (FHE) in practice. The core reason of its good performances is the powerful Programmable Bootstrapping (PBS) operation, that enables to homomorphically evaluate a Look-Up Table (LUT) on a ciphertext while simultaneously reducing its noise. However, the computational cost of running a PBS degrades severely when the size of the plaintext space increases, making it intractable for precision larger than 8 bits. So, evaluating a LUT larger than 28 is not considered possible with the “vanilla” TFHE scheme. In this paper, we propose a technique to accelerate LUT evaluation at high precision, that significantly enhances the state of the art. Our method beats the original PBS for spaces larger than 6 bits, and is competitive with the WoP-PBS (the reference of the state of art) while being conceptually simpler. Additionally, our method relies only on the standard PBS of TFHE, and therefore does not require the design of new advanced homomorphic operators, facilitating its integration into larger homomorphic compilation systems.
},number={3},journal={IACR Transactions on Cryptographic Hardware and Embedded Systems},author={Belaïd, Sonia and Bon, Nicolas and Rivain, Matthieu},year={2026},month=jul,pages={247–278},doi={10.46586/tches.v2026.i3.247-278},}
Development of Optimized Operations for Homomorphic Cryptography
@inproceedings{10.1007/978-3-032-01901-1_17,author={Baudrin, Jules and Bela{\"i}d, Sonia and Bon, Nicolas and Boura, Christina and Canteaut, Anne and Leurent, Ga{\"e}tan and Paillier, Pascal and Perrin, L{\'e}o and Rivain, Matthieu and Rotella, Yann and Tap, Samuel},editor={Tauman Kalai, Yael and Kamara, Seny F.},title={Transistor: a TFHE-Friendly Stream Cipher},booktitle={Advances in Cryptology -- CRYPTO 2025},year={2025},publisher={Springer Nature Switzerland},address={Cham},pages={530--565},isbn={978-3-032-01901-1},url={https://doi.org/10.1007/978-3-032-01901-1_17},doi={10.1007/978-3-032-01901-1_17},}
Further Improvements in AES Execution over TFHE
Sonia
Belaïd, Nicolas
Bon, Aymen
Boudguiga, and
3 more authors
@article{10.62056/ahmp-4tw9,author={Belaïd, Sonia and Bon, Nicolas and Boudguiga, Aymen and Sirdey, Renaud and Trama, Daphné and Ye, Nicolas},title={Further Improvements in {AES} Execution over {TFHE}},volume={2},number={1},year={2025},date={2025-04-08},issn={3006-5496},url={https://doi.org/10.62056/ahmp-4tw9},doi={10.62056/ahmp-4tw9},journal={{IACR} Communications in Cryptology},publisher={International Association for Cryptologic Research},}
Optimized Homomorphic Evaluation of Boolean Functions
Nicolas
Bon, David
Pointcheval, and Matthieu
Rivain
@article{DBLP:journals/tches/BonPR24,author={Bon, Nicolas and Pointcheval, David and Rivain, Matthieu},title={Optimized Homomorphic Evaluation of Boolean Functions},journal={{IACR} Trans. Cryptogr. Hardw. Embed. Syst.},volume={2024},number={3},pages={302--341},year={2024},url={https://doi.org/10.46586/tches.v2024.i3.302-341},doi={10.46586/TCHES.V2024.I3.302-341},timestamp={Wed, 21 Aug 2024 22:05:49 +0200},biburl={https://dblp.org/rec/journals/tches/BonPR24.bib},bibsource={dblp computer science bibliography, https://dblp.org},}