Guillaume Bonnoron

A journey towards practical fully homomorphic encryption

Summary

The objective of this thesis is to study how homomorphic cryptography could be used aboard ships. Since this cryptographic technique allows encrypted data to be processed within a program, it would serve as an additional obstacle for an attacker attempting to steal operational data.

Given the dynamic nature of this topic within the cryptographic community, we focused our research on three main areas:

• First, we took on the role of an attacker to gain a better understanding of how this cryptography could be broken. This led us to design a new attack, based on existing results but within a more targeted framework that improved the state of the art. This work was published at the IndoCrypt 2017 international conference. Through this project, we became involved in the algorithmic cryptanalysis community, particularly in the development of the fplll function library.
• With a solid understanding of attack methodologies, we conducted a comprehensive review of existing homomorphic encryption schemes and compared them. This work, done in collaboration with Vincent Migliore, aims to assist implementers—who may not necessarily be cryptographers—by providing them with precomputed parameter tables (safe and correct) tailored to various use cases.
• Finally, during a doctoral research internship at CWI Amsterdam, Guillaume worked with Léo Ducas and Max Fillinger on the design and implementation of a new homomorphic encryption scheme. This scheme generalizes an existing one while introducing multiple improvements.

Thesis Defense

The final thesis defense took place on March 15, 2018, and Guillaume Bonnoron was awarded a doctorate degree from IMT Atlantique.

The jury consisted of the following members:

• Frederik VERCAUTEREN – Lecturer, KU Leuven Leefdaal, Belgium
• Thomas JOHANSSON – Professor, Lund University, Sweden
• Léo DUCAS – Researcher, CWI, Amsterdam
• Damien STEHLE – Professor, École Normale Supérieure de Lyon
• Renaud SIRDEY – Research Director, CEA/LIST, Gif-sur-Yvette
• Caroline FONTAINE – Researcher, CNRS & IMT Atlantique
• Adeline ROUX-LANGLOIS (Guest) – Researcher, IRISA, Rennes
• Sylvain LACHARTRE (Guest) – Researcher, Thales Communication and Security

Since earning his doctorate, Guillaume Bonnoron has continued his research in the field of cybersecurity.