Xavier BULTEL

		Xavier BULTEL French version About me I am an Associate Professor at INSA CVL (Bourges, France) since 2019, in the SDS team (LIFO). I am also a member of the INRIA team PETSCRAFT since 2024. 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/PETSCRAFT team seminar. Menu Research - Teaching - Miscellaneous - Combinatorial games - Contact

Research My research focuses on cryptography. I work mainly on the design of cryptographic protocols and the provable security, with applications to privacy. 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) 2024 Xavier Bultel "Physical Ring Signature." FUN 2024 (Eprint) Xavier Bultel, Charles Olivier-Anclin "Taming Delegations in Anonymous Signatures: k-Times Anonymity for Proxy and Sanitizable Signature." CANS 2024 (best student paper award) (Eprint) Xavier Bultel, Charles Olivier-Anclin "On the Anonymity of Linkable Ring Signatures." CANS 2024 Xavier Bultel, Charlène Jojon, Pascal Lafourcade "Cryptographic Cryptid Protocols: How to Play Cryptid with Cheaters." CANS 2024 (Eprint) 2023 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) 2022 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) 2021 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 2020 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) 2019 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) 2018 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) 2017 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) 2016 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)

Teaching 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.

Miscellaneous Phd students: Charles Olivier-Anclin (2022-) co-supervised with Pascal Lafourcade and Mirko Koscina. Charlène Jojon (2023-) co-supervised with Benjamin Nguyen. Khourédia Cisse (2024-) co-supervised with Benjamin Nguyen. 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: ACNS 2025, SECRYPT 2023, IMACC23, APKC 2021, PST 2019, WISTP 2019, WISTP 2018 Seminar invitations: 06/02/2024 - Séminaire Protection de l'Information, Codage, Cryptographie (XLIM, Limoges) Preuves à divulgation nulle génériques sur des chiffrements : outils pour la pédagogie et la médiation scientifique. 21/02/2023 - Seminar of the Cryptography Group at Royal Holloway (Royal Holloway, London, UK) Generic Zero-Knowledge Proofs on Ciphertexts – Tools for Pedagogy and Popular Science. 30/01/2020 - CITI seminar (CITI Lab, Privatics, Lyon) Sécurité des protocoles de jeux de levées : comment jouer au Bridge avec des tricheurs. 14/052016 - Séminaire Protection de l'Information, Codage, Cryptographie (XLIM, Limoges) A Posteriori Openable Public Key Encryption. Popular science: 12-13/10/2024 - Stand at "la fête de la science" about the Enigma machine and the Turing bombe. 16/02/2024 - Talk to high school teachers about proofs and e-voting for the "journée des labos de maths du Cher". 5/12/2023 - Talk to high school students about proofs and e-voting for the "semaine de l'informatique". 15-16/10/2022 - Stand at "la fête de la science" about zero-knowledge proof and e-voting. Since 2022 - Co-animation of the "MATh.en.JEANS" workshop (in collaboration with the Marguerite de Navarre high school.) 16/12/2021 - Talk to high school students about proofs and e-voting for the "MATh.en.JEANS" workshop Events organisation: 2020 - Local co-organisation of the "15ème Journée Informatique de la Région Centre Val de Loire. (JIRC)" at INSA CVL.

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 : Play Duolitaire online Play Shooting Star on Android

Contact INSA-CVL 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.