About

I am a Research Associate in Cryptography (postdoctoral position) in the Department of Informatics at King’s College London in the Cryptography team.

Previously, I was a PhD student in the AriC team in the LIP laboratory in the ENS de Lyon, in France, working under the supervision of Damien Stehlé, Guillaume Hanrot and Bruno Salvy, funded by the Direction Générale de l’Armement (Pôle de Recherche CYBER).

I am currently mainly interested in algorithmic (classical and quantum) on structured lattices (e.g. ideals or module lattices), and their applications to cryptography.

Research Work

Talks

• A Gaussian Leftover Hash Lemma for Modules over Number Fields the 09/10/2025 at Grace seminar. [slides].
• Ideal-SVP is Hard for Small-Norm Uniform Prime Ideals the 26/09/2023 at CANARI seminar. [slides].
• NTRU and Module uSVP of rank 2 the 13/04/2022 at Journées C2 2022. [slides].

Published work

• A Gaussian Leftover Hash Lemma for Modules over Number Fields. Martin R. Albrecht, Joël Felderhoff, Russell W. F. Lai, Oleksandra Lapiha and Ivy K. Y. Woo. Eurocrypt 2026. [Full Version]. [Mirror].
• Hardness of Structured Lattice Problems for Post-Quantum Cryptography. Joël Felderhoff. PhD Thesis. [Manuscript]. [Mirror]. [Slides] [Defense Information].
• Ideal-SVP is Hard for Small-Norm Uniform Prime Ideals. Joël Felderhoff, Alice Pellet-Mary, Damien Stehlé and Benjamin Wesolowski. TCC 2023. [Full Version]. [Mirror]
• On Module Unique-SVP and NTRU. Joël Felderhoff, Alice Pellet-Mary and Damien Stehlé. ASIACRYPT 2022. [Full Version]. [Mirror]

Preprints

• Quantumly Computing S-unit Groups in Quantified Polynomial Time and Space. Koen de Boer and Joël Felderhoff. [Link]. [Mirror]

Other

• Round Table Politique, cryptographie et nouvelles régulations. Journées Code et Cryptographie 2023.

Unpublished work

• A CHSP Oracle for Arakelov Class Group. Research Internship supervised by Léo Ducas in Crypto group, CWI, Amsterdam. Feb-July 2021. [report (eprint version)].
• Impossibility results for Module LLL based on Euclidean Division. Research Internship supervised by Damien Stehlé in AriC team, LIP, ENS de Lyon. Sept 2020-Feb 2021. [report].
• Hard Homogenous Spaces and Commutative Supersingular Isogeny based Diffie–Hellman. Research Internship supervised by Benjamin Smith in Grace team, Laboratoire d’Informatique de l’École Polytechnique. Summer 2019. [report].
• Homological product code and weight of random tensors. Research Internship supervised by Péter Vrana in QMATH team, Department of Mathematical Sciences of the University of Copenhagen. Summer 2018. [report].
• Walking along the infrastructures of real quadratic and pure cubic fields. Research Internship supervised by Pierre Jean Spaenlehauer in CARAMBA team, INRIA Nancy - Grand Est. Summer 2017. [report].