Thomas Prest

Intro

I am Head of Research at PQShield. Before that, I was an engineer at Thales. Still before it, I completed a PhD at the École Normale Supérieure. My main fields of interest are post-quantum cryptography and discrete algorithms, however I am open to most topics related to cryptography.

Before contacting me:

I will take no journal review or program committee membership in 2025. I might take subreviews in exceptional circumstances.
PQShield's Research team is not hiring permanent researchers at the moment (until 01/01/2026), however we welcome applications for internships, PhD students and post-docs.
If you would like to discuss technical questions, feel free to suggest a 15-30 minutes online meeting to discuss them (I suggest Google Meet).
I have poor facial memory, so apologies if we have met before and I don't recognise you.

Publications

Triple Ratchet: A Bandwidth Efficient Hybrid-Secure Signal Protocol - EUROCRYPT 2025
joint work with Yevgeniy Dodis, Daniel Jost, Shuichi Katsumata and Rolfe Schmidt
Flood and Submerse: Distributed Key Generation and Robust Threshold Signature from Lattices - CRYPTO 2024
joint work with Thomas Espitau and Guilhem Niot
Raccoon: A Masking-Friendly Signature Proven in the Probing Model - CRYPTO 2024
joint work with Rafael del Pino, Shuichi Katsumata and Mélissa Rossi
Plover: Masking-Friendly Hash-and-Sign Lattice Signatures - EUROCRYPT 2024
joint work with Muhammed Esgin, Thomas Espitau, Guilhem Niot, Amin Sakzad and Ron Steinfeld
Threshold Raccoon: Practical Threshold Signatures from Standard Lattice Assumptions - EUROCRYPT 2024
joint work with Rafael del Pino, Shuichi Katsumata, Mary Maller, Fabrice Mouhartem and Markku-Juhani Saarinen
High-Order Masking of Lattice Signatures in Quasilinear Time - IEEE Symposium on Security and Privacy, 2023
joint work with Rafaël del Pino, Mélissa Rossi and Markku-Juhani O. Saarinen
A Key-Recovery Attack against Mitaka in the t-Probing Model - PKC 2023
How to Hide MetaData in MLS-Like Secure Group Messaging: Simple, Modular, and Post-Quantum - CCS 2022
joint work with Keitaro Hashimoto and Shuichi Katsumata
A Concrete Treatment of Efficient Continuous Group Key Agreement via Multi-Recipient PKEs () - CCS 2021
joint work with Keitaro Hashimoto, Shuichi Katsumata, Eamonn Postlethwaite and Bas Westerbaan
Probing Security through Input-Output Separation and Revisited Quasilinear Masking - CHES 2021
joint work with Dahmun Goudarzi, Matthieu Rivain and Damien Vergnaud
SoK: How (not) to Design and Implement Post-Quantum Cryptography - CT-RSA 2021
joint work with James Howe and Daniel Apon
An Efficient and Generic Construction for Signal's Handshake (X3DH): Post-Quantum, State Leakage Secure, and Deniable () - PKC 2021
joint work with Keitaro Hashimoto, Shuichi Katsumata and Kris Kwiatkowski
Exact Lattice Sampling from Non-Gaussian Distributions - PKC 2021
joint work with Maxime Plançon
Scalable Ciphertext Compression Techniques for Post-Quantum KEMs and their Applications - ASIACRYPT 2020
joint work with Shuichi Katsumata, Kris Kwiatkowski and Federico Pintore
Cryptographic Divergences: New Techniques and New Applications - SCN 2020
joint work with Marc Abboud
ModFalcon: compact signatures based on module NTRU lattices - AsiaCCS 2020
joint work with Chitchanok Chuengsatiansup, Damien Stehlé, Alexandre Wallet and Keita Xagawa
Integral Matrix Gram Root and Lattice Gaussian Sampling without Floats - EUROCRYPT 2020
joint work with Léo Ducas, Steven Galbraith and Yang Yu
Isochronous Gaussian Sampling: From Inception to Implementation () - PQCrypto 2020
joint work with James Howe, Thomas Ricosset and Mélissa Rossi
Simple, Fast and Constant-Time Gaussian Sampling over the Integers for Falcon - Second PQC Standardization Conference (superseded by the work above)
joint work with Thomas Ricosset and Mélissa Rossi
Unifying Leakage Models on a Rényi Day () - CRYPTO 2019
joint work with Dahmun Goudarzi, Ange Martinelli and Alain Passelègue
More Efficient Algorithms for the NTRU Key Generation using the Field Norm - PKC 2019
joint work with Thomas Pornin
Grafting Trees: a Fault Attack against the SPHINCS framework - PQCRYPTO 2018
joint work with Laurent Castelnovi and Ange Martinelli
Sharper Bounds in Lattice-Based Cryptography using the Rényi Divergence - ASIACRYPT 2017
Fast Fourier Orthogonalization () - ISSAC 2016
joint work with Léo Ducas
Quadratic Time, Linear Space Algorithms for Gram-Schmidt Orthogonalization and Gaussian Sampling in Structured Lattices () - EUROCRYPT 2015
joint work with Vadim Lyubashevsky
Efficient Identity-Based Encryption over NTRU Lattices () - ASIACRYPT 2014
joint work with Léo Ducas and Vadim Lyubashevsky
Non-Linear Polynomial Selection for the Number Field Sieve - Journal of Symbolic Computation, Volume 47 Issue 4, April 2012
joint work with Paul Zimmermann

PhD Thesis

Gaussian Sampling in Lattice-Based Cryptography - École Normale Supérieure
Supervised by Vadim Lyubashevsky and David Pointcheval
Defended on December 2015

Talks (since 2017)

Secret Sharing Schemes for Lattice-Based Threshold Cryptography -
Workshop on the mathematics of post-quantum cryptography (02-06-2025)
Secret Sharing Schemes for Lattice-Based Threshold Cryptography -
WRACH 2025 (25-04-2025)
Masking-Friendly Lattice Schemes and Lattice-Friendly Masking Schemes (Keynote) -
CASCADE 2025 (03-04-2025)
Lattice-Based Threshold Signatures: Into The Raccoonverse -
Emerging topics in design and cryptanalysis of post-quantum schemes (6-11-2024)
Attacking and Protecting SLH-DSA against Fault Injection -
Deployment of post-quantum cryptography (11-10-2024)
Attaques par fautes sur SLH-DSA -
JAIF 2024 (1-10-2024)
Post-Quantum Secure Messaging -
Graz Security Week (24-09-2024)
Raccoon: A Masking-Friendly Signature Proven in the Probing Model -
CRYPTO 2024 (21-08-2024)
How Multi-Recipient KEMs can help the Deployment of Post-Quantum Cryptography -
Fifth PQC Standardization Conference (12-04-2024)
Threshold Raccoon -
Fifth PQC Standardization Conference (11-04-2024)
Falcon -
Fifth PQC Standardization Conference (10-04-2024)
More Efficient Protocols for Post-Quantum Secure Messaging -
Real World Crypto 2024 (26-03-2024)
Masking-Friendly Signatures and the Design of Raccoon -
Aarhus Crypto Seminar (13-09-2023)
Raccoon -
2nd Oxford Post-Quantum Cryptography Summit 2023 (05-09-2023)
The Design of Falcon -
Cryptography Standard Design Seminar (02-07-2023)
Falcon -
Journées du PEPR PQ‐TLS du PEPR Quantique (29-06-2023)
A Key-Recovery Attack against Mitaka in the t-Probing Model -
PKC 2023 (pre-recorded)
Falcon -
Real World PQC (26-03-2023)
A Post-Quantum Construction for Signal's Handshake (X3DH)
9th ETSI/IQC Quantum Safe Cryptography Event (15-02-2023)
An Efficient and Generic Construction for Signal’s Handshake (X3DH) -
4th PQC Standardization Conference (01-12-2022)
Falcon -
4th PQC Standardization Conference (29-11-2022)
Secure Messaging in a Post-Quantum World -
PQShield Webinar (22-11-2022)
Falcon
Symposium Post-Quantum Cryptography - Episode IV (15-11-2022)
Lattice-Based Signatures -
PQCifris 2022 Workshop (12-10-2022)
Post-Quantum Multi-Recipient KEMs and their Applications
Algebraic Coding and Cryptography on the East coast Seminar Series (ACCESS) (4-10-2022)
A Concrete Treatment of Efficient Continuous Group Key Agreement via Multi-Recipient PKEs - (FR) (EN)
Séminaire de Cryptographie de l'Université de Rennes 1 (19-11-2021)
Lattice-based NIST Candidates - Abstractions and Ninja Tricks -
Mise en Œuvre de la Cryptographie Post-Quantique (European Cyber Week) (17-11-2021)
Basic Lattice Constructions (2-hour crash course) - (1/2) (2/2)
ASCRYPTO Summer School (05-10-2021)
Post-Quantum X3DH -
Post-Quantum Networks Workshop (30-09-2021)
Post-Quantum Multi-Recipient KEMs and their Applications -
2021 EWHA-KMS International Workshop on Cryptography (24-06-2021)
f-Divergences in Statistical Security Proofs -
2021 EWHA-KMS International Workshop on Cryptography (23-06-2021)
Falcon -
Third PQC Standardization Conference (07-06-2021)
SoK: How (not) to Design and Implement Post-Quantum Cryptography -
The Cryptographer's Track at the RSA Conference (19-05-2021)
Lattice-based NIST Candidates - Abstractions and Ninja Tricks -
SemSecuElec Seminar (DGA × Inria) (23-04-2021)
Ciphertext Compression for Post-Quantum KEMs and Application to Group Messaging -
ETSI Quantum Safe Cryptography Technical Event (18-02-2021)
Scalable Ciphertext Compression Techniques for Post-Quantum KEMs and their Applications
Weekly seminar of the Applied Cryptography group at ETH Zurich (20-01-2021)
Scalable Ciphertext Compression Techniques for Post-Quantum KEMs and their Applications -
Joint Online Crypto Seminar (18-01-2021)
Scalable Ciphertext Compression Techniques for Post-Quantum KEMs and their Applications -
ASIACRYPT (02-12-2020)
Sampling in Polynomial Lattices, and Applications -
Lattices: From Theory to Practice (29-04-2020)
Unifying Leakage Models on a Rényi Day
Séminaire de Cryptographie de l'Université de Rennes 1 (20-09-2019)
Falcon - An Update -
Second PQC Standardization Conference (23-08-2019)
Unifying Leakage Models on a Rényi Day -
CRYPTO (19-08-2019)
Unifying Leakage Models on a Rényi Day -
Fifth London Symposium on Information Theory (LSIT) (31-05-2019)
All Along the Ring Tower: Algebraic Structures for Fun and Profit -
RISC + PROMETHEUS Seminar (CWI Cryptology Group) (03-05-2019)
More Efficient Algorithms for the NTRU Key Generation using the Field Norm -
PKC 2019 (17-04-2019)
Unifying Leakage Models on a Rényi Day
Seminar of the Information Security Group (Royal Holloway) (14-01-2019)
Unifying Leakage Models on a Rényi Day
AriC's Weekly Crypto Session (13-12-2018)
Solving Generalized Bézout Equations using the Field Norm and Applications to NTRU
Séminaire LJK-Modèles et Algorithmes Déterministes: CASYS (12-12-2018)
Solving Generalized Bézout Equations using the Field Norm and Applications to NTRU
Séminaire Calcul Formel du XLIM (11-10-2018) -
Falcon
Séminaire Protection de l'Information, Codage, Cryptographie du XLIM (09-10-2018)
Candidats à base de réseaux euclidiens
Les Enjeux du Post-Quantique (06-09-2018)
Falcon: Compact lattice-based signatures based on the hash & sign paradigm
Oxford Cryptography Seminar (30-05-2018)
Falcon -
First PQC Standardization Conference (12-04-2018)
Grafting Trees: a Fault Attack against the SPHINCS framework -
PQCrypto 2018 (10-04-2018)
Grafting Trees: a Fault Attack against the SPHINCS framework -
CryptoAction Symposium 2018 (04-04-2018)
The Rényi Divergence and Security Proofs -
Lattice Coding & Crypto Meeting (Royal Holloway) (26-03-2018)
Falcon (hard problems, attacks, features) -
Seminar on Quantum-Safe Cryptography (PolSys) (16-02-2018)
Falcon (algorithmics) -
Combined event on Post-Quantum Cryptography (31-01-2018)
Solving Bézout Equations using the Field Norm and Applications to NTRU
ENS Lyon's Lattice Meetings (19-01-2018)
A journey in the land of (hash-and-sign) lattice-based signatures (keynote) -
16th IMA International Conference on Cryptography and Coding (14-12-2017)
Sharper Bounds in Lattice-Based Cryptography using the Rényi Divergence -
ASIACRYPT 2017 (04-12-2017)
Sharper Bounds in Lattice-Based Cryptography using the Rényi Divergence
Seminar of the Project-team Grace at INRIA and Polytechnique (16-06-2017)
Easier floating-point on a Rényi day
ENS Lyon's Lattice Meetings (11-05-2017)
The Falcon signature scheme
ENS Lyon's Lattice Meetings (11-05-2017)
Overview of quantum-safe cryptography II
Quantum-Safe Cryptography for Industry (QsCI) (30-04-2017)
Les signatures sur les réseaux euclidiens (keynote)
Journées Codage & Cryptographie 2017 (25-01-2017)

Falcon

In 2016, NIST launched a standardization process to replace the current public-key cryptographic algorithms with post-quantum solutions. In July 2022, Falcon was selected as one of the three signature standards. Out of the three standards, Falcon is the one with the lowest communication cost (added sizes of a public key and a signature).

Falcon is a joint work with a team of talented cryptographers, cryptanalysts and implementers: Pierre-Alain Fouque, Jeffrey Hoffstein, Paul Kirchner, Vadim Lyubashevsky, Thomas Pornin, Thomas Ricosset, Gregor Seiler, William Whyte and Zhenfei Zhang.

Students

Past

Laurent Castelnovi - Université de Limoges
Master Internship 2017 -
Mélissa Rossi - Thales / École Normale Supérieure / ANSSI
PhD 2017-2020
Marc Abboud - École Normale Supérieure
Master Internship 2019
Maxime Plançon - École Normale Supérieure de Cachan
Master Internship 2019 + ARPE 1-Year Internship 2019-2020
Mario Marhuenda Beltran - École normale supérieure Paris-Saclay
Master Internship 2022
Guilhem Niot - École normale supérieure de Lyon
PhD Student 2023-2025, co-supervised with Pierre-Alain Fouque