French version

About me

I am Associate Professor at INSA CVL (Bourges, France) since 2019, in the SDS team (LIFO). Before that, I was a Post-doctoral Researcher at IRISA (team EMSEC) at Université Rennes 1. I completed my PhD at Université Clermont Auvergne in may 2018. My manuscript is available here.

I am also the organiser of the SDS team seminar.



My research focuses on cryptography. I work mainly on the design of cryptographic protocols and the provable security. My interests include general cryptographic primitives, the design of specific applied protocols, and the study of the security of real-world protocols such as TLS or Signal.

Publications (dblp)


  • Xavier Bultel
    "Physical Ring Signature"
    FUN 2024 (to appear, Eprint)


  • Rohann Bella, Xavier Bultel, Céline Chevalier, Pascal Lafourcade, Charles Olivier-Anclin
    "Practical Construction for Secure Trick-Taking Games Even With Cards Set Aside"
    FC 2023 ( Eprint)


  • Xavier Bultel
    "CCA Secure A Posteriori Openable Encryption in the Standard Model." CT-RSA 2022 (Eprint)
  • Xavier Bultel, Cristina Onete
    "Pairing-free secure-channel establishment in mobile networks with fine-grained lawful interception." SAC 2022, short paper (Eprint)
  • Xavier Bultel
    "Enseigner les preuves à divulgation nulle sur des chiffrements sans prérequis d'arithmétique."
    RESSI 2022 (Eprint)
  • Xavier Bultel
    "Zero-Knowledge Proof of Knowledge for Peg Solitaire." FUN 2022 (Paper)
  • Xavier Bultel, Ashley Fraser, Elizabeth A. Quaglia
    "Improving the Efficiency of Report and Trace Ring Signatures." SSS 2022 (Paper)


  • Angèle Bossuat, Xavier Bultel
    "Unlinkable and Invisible γ-Sanitizable Signatures." ACNS 2021 (best student paper award) (Eprint)
  • Olivier Blazy, Xavier Bultel, Pascal Lafourcade, Octavio Perez Kempner
    "Generic Plaintext Equality and Inequality Proofs." FC 2021 (Eprint)
  • Ghada Arfaoui, Olivier Blazy, Xavier Bultel, Pierre-Alain Fouque, Thibaut Jacques, Adina Nedelcu, Cristina Onete
    "How to (legally) keep secrets from mobile operators." ESORICS 2021 (Eprint)
  • Xavier Bultel, Pascal Lafourcade, Charles Olivier-Anclin, Leo Robert
    "Generic Construction for Identity-based Proxy Blind Signature." FPS 2021


  • Xavier Bultel, Jannik Dreier, Jean-Guillaume Dumas, Pascal Lafourcade,
    "A Faster Cryptographer's Conspiracy Santa." Theoretical Computer Science (Eprint)
  • Angèle Bossuat, Xavier Bultel, Pierre-Alain Fouque, Cristina Onete, Thyla van der Merwe
    "Designing Reverse Firewalls for the Real World." ESORICS 2020 (Eprint)


  • Xavier Bultel, Pascal Lafourcade,
    "Secure Trick-Taking Game Protocols: How to Play Online Spades with Cheaters." FC 2019 (Eprint)
  • Xavier Bultel, Pascal Lafourcade, Russell W. F. Lai, Giulio Malavolta, Dominique Schröder, Sri Aravinda Krishnan Thyagarajan
    "Efficient Invisible and Unlinkable Sanitizable Signatures." PKC 2019 (Eprint)
  • Olivier Blazy, Angèle Bossuat, Xavier Bultel, Pierre-Alain Fouque, Cristina Onete, Elena Pagnin
    "SAID: Reshaping Signal into an Identity-Based Asynchronous Messaging Protocol with Authenticated Ratcheting." EuroS&P 2019 (Eprint)
  • Ghada Arfaoui, Xavier Bultel, Pierre-Alain Fouque, Adina Nedelcu, Cristina Onete
    "The privacy of the TLS 1.3 protocol." PoPETs 2019 (Eprint)


  • Xavier Bultel, Radu Ciucanu, Matthieu Giraud, Pascal Lafourcade, Lihua Ye
    “Secure Joins with MapReduce.” FPS 2018 (best paper award) (Eprint)
  • Xavier Bultel, Jannik Dreier, Matthieu Giraud, Marie Izaute, Timothée Kheyrkhah, Pascal Lafourcade, Dounia Lakhzoum, Vincent Marlin, Ladislav Moták
    "Security analysis and psychological study of authentication methods with PIN codes." RCIS 2018 (Eprint)
  • Xavier Bultel, Jannik Dreier, Jean-Guillaume Dumas, Pascal Lafourcade, Daiki Miyahara, Takaaki Mizuki, Atsuki Nagao, Tatsuya Sasaki, Kazumasa Shinagawa, Hideaki Sone
    "Physical Zero-Knowledge Proof for Makaro." SSS 2018 (Eprint)
  • Xavier Bultel, Jannik Dreier, Jean-Guillaume Dumas, Pascal Lafourcade,
    "A Cryptographer's Conspiracy Santa." FUN 2018 (Eprint)


  • Gildas Avoine, Xavier Bultel, Sébastien Gambs, David Gerault, Pascal Lafourcade, Cristina Onete, Jean-Marc Robert,
    "A Terrorist-fraud Resistant and Extractor-free Anonymous Distance-Bounding Protocol." AsiaCCS 2017 (Eprint)
  • Xavier Bultel, Radu Ciucanu, Matthieu Giraud, Pascal Lafourcade
    "Secure Matrix Multiplication with MapReduce." ARES 2017 (Eprint)
  • Xavier Bultel, Pascal Lafourcade
    "Unlinkable and Strongly Accountable Sanitizable Signatures from Verifiable Ring Signatures."
    CANS 2017 (Eprint)
  • Xavier Bultel, Manik Lal Das, Hardik Gajera, David Gérault, Matthieu Giraud, Pascal Lafourcade
    "Verifiable Private Polynomial Evaluation." ProvSec 2017 (Eprint)
  • Xavier Bultel, Jannik Dreier, Pascal Lafourcade, Malika More
    "How to explain modern security concepts to your children." Cryptologia (Eprint)


  • Xavier Bultel, Pascal Lafourcade,
    "A Posteriori Openable Public Key Encryption." IFIP SEC 2016 (Eprint)
  • Xavier Bultel, Sébastien Gambs, David Gerault, Pascal Lafourcade, Cristina Onete, Jean-Marc Robert,
    "A Prover-Anonymous and Terrorist-Fraud Resistant Distance Bounding Protocol." WiSec 2016 (Eprint)
  • Olivier Blazy, Xavier Bultel, Pascal Lafourcade,
    "Two Secure Anonymous Proxy-based Data Storages." SECRYPT 2016, short paper (Eprint)
  • Xavier Bultel, Pascal Lafourcade,
    "k-time Full Traceable Ring Signature." ARES 2016 (Eprint)
  • Olivier Blazy, Xavier Bultel, Pascal Lafourcade,
    "Anonymizable Ring Signature Without Pairing." FPS 2016 (Eprint)
  • Xavier Bultel, Jannik Dreier, Jean-Guillaume Dumas, Pascal Lafourcade,
    "Physical Zero-Knowledge Proofs for Akari, Takuzu, Kakuro and KenKen." FUN 2016 (Eprint)


I teach at the INSA CVL, speciality Computer Security and Technologies (STI) and Industrial Risk Control (MRI):

STI 3rd year : Error correcting codes (CM/TD)
MRI 3rd year : Operating systems (TP)
STI 4th year : Cryptography (CM/TD)
MRI 3rd year : C++ (CM/TD)
STI 4th/5th year : Advanced cryptography (CM/TD)

In previous years, I have also taught in the following modules:

2nd year : Algorithm and programming (TD/TP).
STI 3rd year : Web (TD)
STI 3rd year : Operating systems (CM/TD)

From 2014 to 2017, I taught at the "networks and telecommunications" department (IUT Clermont-Ferrand):

Licences 3 pro : Operating system for networks.
DUTs 1 : Operating system, Programming, web.


Phd students:

Projects :

  • ANR PRIVA-SIQ (2024-2028) this project is coordinated by Cristina Onete (XLIM, Limoges). I am scientific leader of the project at INSA CVL.

PC Member:

SECRYPT 2023, IMACC23, APKC 2021, PST 2019, WISTP 2019, WISTP 2018

Seminar invitations:

  • 2023 - Seminar of the Cryptography Group at Royal Holloway (Royal Holloway, London, UK)
    Generic Zero-Knowledge Proofs on Ciphertexts – Tools for Pedagogy and Popular Science.
  • 2020 - CITI seminar (CITI Lab, Privatics, Lyon)
    Sécurité des protocoles de jeux de levées : comment jouer au Bridge avec des tricheurs.
  • 2016 - Séminaire Protection de l'Information, Codage, Cryptographie (XLIM, Limoges)
    A Posteriori Openable Public Key Encryption.

Popular science:

  • 2022 - Stand at "la fête de la science" about zero-knowledge proof and e-voting.
  • 2022-2023 - Co-animation of the "MATh.en.JEANS" workshop (in collaboration with the Marguerite de Navarre high school.)
  • 2021 - Talk to high school students about proofs and e-voting for the "MATh.en.JEANS" workshop

Events organisation:

Combinatorial games

In my free time, I enjoy playing combinatorial board games. I have created some myself. Implementing this kind of games is a good algorithmic exercise, so I offer INSA CVL students to implement my games for their third year programming project. The goal is to propose an interface and an artificial intelligence for a given game. Feel free to try some of these games :


88 boulevard Lahitolle
CS 60013 - 18022 Bourges CEDEX

Mail : xavier dot bultel at insa-cvl dot fr

Bonus : try my computer science paper title generator here.