2023Activity reportProject-TeamCASCADE

RNSR: 200818333X
  • Research center Inria Paris Centre
  • In partnership with:CNRS, Ecole normale supérieure de Paris
  • Team name: Construction and Analysis of Systems for Confidentiality and Authenticity of Data and Entities
  • In collaboration with:Département d'Informatique de l'Ecole Normale Supérieure
  • Domain:Algorithmics, Programming, Software and Architecture
  • Theme:Algorithmics, Computer Algebra and Cryptology


Computer Science and Digital Science

  • A4. Security and privacy
  • A4.3. Cryptography
  • A4.3.1. Public key cryptography
  • A4.3.2. Secret key cryptography
  • A4.3.3. Cryptographic protocols
  • A4.3.4. Quantum Cryptography
  • A4.8. Privacy-enhancing technologies
  • A7. Theory of computation
  • A7.1.4. Quantum algorithms
  • A8.5. Number theory
  • A8.9. Performance evaluation
  • A8.10. Computer arithmetic

Other Research Topics and Application Domains

  • B6.4. Internet of things
  • B9.5.1. Computer science
  • B9.10. Privacy

1 Team members, visitors, external collaborators

Research Scientists

  • David Pointcheval [Team leader, CNRS, Senior Researcher, HDR]
  • Francesco Arzani [INRIA, Advanced Research Position, from Sep 2023, QAT AEx Team]
  • Ulysse Chabaud [INRIA, Researcher, from Feb 2023, QAT AEx Team]
  • Jianwei Li [INRIA, Starting Research Position]
  • Brice Minaud [INRIA, Researcher]
  • Phong-Quang Nguyen [INRIA, Senior Researcher, HDR]
  • Harold Ollivier [INRIA, Senior Researcher, QAT AEx Team]
  • Mathys Rennela [INRIA, Starting Research Position, QAT AEx Team]

Faculty Member

  • Céline Chevalier [UNIV PARIS II, Associate Professor, Conventionnée ENS Paris, HDR]

Post-Doctoral Fellows

  • Jack Davis [INRIA, Post-Doctoral Fellow, from Oct 2023, QAT AEx Team]
  • Wissam Ghantous [INRIA, Post-Doctoral Fellow, from Sep 2023]
  • Florette Martinez [ENS PARIS, from Sep 2023]

PhD Students

  • Sami Abdul Sater [INRIA, from Oct 2023, QAT AEx Team]
  • Leonard Assouline [ENS PARIS]
  • Henry Bambury [DGA]
  • Hugo Beguinet [THALES, CIFRE]
  • Baptiste Cottier [INRIA, until Jan 2023]
  • Paola De Perthuis [COSMIAN, CIFRE]
  • Lénaïck Gouriou [LEANEAR, until May 2023]
  • Paul Hermouet [Univ. Paris II]
  • Guirec Lebrun [ANSSI]
  • Ngoc Ky Nguyen [ENS PARIS]
  • Rajarsi Pal [INRIA, from Dec 2023, QAT AEx Team]
  • Michael Reichle [INRIA, until Sep 2023]
  • Eric Sageloli [Univ. Paris II et THALES, from May 2023]
  • Robert Schädlich [ENS PARIS]
  • Hugo Senet [ENS PARIS, until Sep 2023]
  • Quoc Huy Vu [Univ. Paris II, until Feb 2023]

Administrative Assistants

  • Meriem Guemair [INRIA]
  • Diana Marino Duarte [INRIA, from Mar 2023]

2 Overall objectives

2.1 Presentation

Cryptographic algorithms are the equivalent of locks, seals, and identification documents over the Internet. They are essential to protect our online bank transactions, medical and personal information, and to support e-commerce and e-government. They come in different flavors. Encryption algorithms are necessary to protect sensitive information from prying eyes. Digital signature algorithms (in combination with hash functions) and MAC algorithms replace hand-written signatures in electronic transactions. Identification protocols allow to securely verify the identity of a remote party. As a whole, cryptology is a research area with a high strategic impact in industry, for individuals, and for society. The research activity of project-team CASCADE addresses the following topics, which cover most of the areas that are currently active in the international cryptographic community, with a focus on public-key algorithms:

  1. Algorithm and protocol design, with provable security;
  2. Theoretical and practical attacks.

2.2 Design of Provably Secure Primitives and Protocols

Since the beginning of public-key cryptography, with the seminal Diffie-Hellman paper, many suitable algorithmic problems for cryptography have been proposed and many cryptographic schemes have been designed, together with more or less heuristic proofs of their security relative to the intractability of the underlying problems. However, many of those schemes have thereafter been broken. The simple fact that a cryptographic algorithm withstood cryptanalytic attacks for several years has often been considered as a kind of validation procedure, but schemes may take a long time before being broken. As a consequence, the lack of attacks at some time should never be considered as a full security validation of the proposal.

A completely different paradigm is provided by the concept of “provable” security. A significant line of research has tried to provide proofs in the framework of computational complexity theory (a.k.a. “reductionist” security proofs): the proofs provide reductions from a well-studied problem (factoring, RSA or the discrete logarithm) to an attack against a cryptographic protocol.

At the beginning, researchers just tried to define the security notions required by actual cryptographic schemes, and then to design protocols which could achieve these notions. The techniques were directly derived from complexity theory, providing polynomial reductions. However, their aim was essentially theoretical. They were indeed trying to minimize the required assumptions on the primitives (one-way functions or permutations, possibly trapdoor, etc), without considering practicality. Therefore, they just needed to design a scheme with polynomial-time algorithms, and to exhibit polynomial reductions from the basic mathematical assumption on the hardness of the underlying problem to an attack of the security notion, in an asymptotic way. However, such a result has no practical impact on actual security. For many years, more efficient reductions have been expected, under the denomination of either “exact security" or “concrete security”, which provide more practical security results, with concrete efficiency properties.

To this aim, a cryptographer has to deal with the following four important steps, which are all main goals of ours:

  • computational assumptions,
    which are the foundation of the security. We thus need to have a strong evidence that the computational problems are reasonably hard to solve, for concrete parameters;
  • security model,
    which makes precise the security notions one wants to achieve, as well as the means the adversary may be given. We contribute to this point, in several ways:
    • by providing security models for many primitives and protocols;
    • by enhancing some classical security models;
    • by considering new means for the adversary.
  • design
    of new schemes/protocols, or more efficient ones, with additional features, etc.
  • security proof,
    which consists in exhibiting a reduction.

2.3 Attacks and security analysis

But, some schemes are still published without complete security proofs, hence their security requires further analysis, and attacks may be found. And even for provably secure schemes, attacks are not excluded, and may appear at several levels:

  • A computational assumption may prove wrong. So we study them, and in particular the ones that are believed to resist quantum computers.
  • the security model may be inappropriate, and allow for devastating attacks in concrete usage scenarios.

3 Research program

3.1 Quantum-safe cryptography

The security of almost all public-key cryptographic protocols in use today relies on the presumed hardness of problems from number theory such as factoring and computing discrete logarithms. This is problematic because these problems have very similar underlying structure, and its unforeseen exploit can render all currently used public-key cryptography insecure. This structure was in fact exploited by Shor to construct efficient quantum algorithms that break all hardness assumptions from number theory that are currently in use. And so naturally, an important area of research is to build provably secure protocols based on mathematical problems that are unrelated to factoring and discrete log. One of the most promising directions in this line of research is using lattice problems as a source of computational hardness, which also offer features that other alternative public-key cryptosystems (such as MQ-based, code-based, isogeny-based or hash-based schemes) cannot provide. The ERC Advanced Grant PARQ aims at evaluating the security of lattice-based cryptography, with respect to the most powerful adversaries, such as quantum computers and large-scale parallel computers.

In the meantime, although a universal quantum computer may be some decades in the future, quantum communication and quantum error correcting codes are beginning to become concretely available. It is already possible to prepare, manipulate and precisely control systems involving a few quantum information bits (qubits). Such quantum technologies could help improve the efficiency and security of concrete cryptographic protocols. The ANR JCJC project CryptiQ aims at considering three possible scenarios (first, the simple existence of a quantum attacker, then the access to quantum communication for anyone, and finally a complete quantum world) and studies the consequences on the cryptographic protocols currently available. This implies elaborating adversarial models and designing or analyzing concrete protocols with formal security proofs, in order to get ready as soon as one of these scenarios becomes the new reality.

3.2 Computations on encrypted data

In the area of computations on encrypted data, there are three main families of approaches:

  • Advanced Encryption,
    with fully homomorphic encryption and functional encryption:
    • Fully Homomorphic Encryption (FHE), which has been announced in 2009, allows to perform any computation on encrypted data, getting the result encrypted under the same key. This is perfect in order to outsource computation in the Cloud, on encrypted data: the Cloud provider does not learn any information;
    • Functional Encryption (FE), proposed in 2011, allows an authority to deliver functional decryption keys, for any function f of his choice, so that on the encryption of any message m, the functional decryption key leads to f(m). This is a generalization of Identity-Based Encryption (IBE), Attribute-Based Encryption (ABE) and Predicate Encryption (PE), which where limited to the identity function, under some access-control.
  • Secure Multi-Party Computation (SMPC)
    is an interactive protocol between 2 or more parties, with their own private inputs. After several communications, this is possible to let each party to learn specific evaluations on the inputs, and nothing else.
  • Searchable Symmetric Encryption (SSE)
    proposes a trade-off between efficiency and security, using fast (structured) symmetric encryption, but allowing some leakage of information. The goal is akin to private information retrieval: one can retrieve records in a database without leaking much information about the query.

4 Application domains

4.1 Privacy for the Cloud

Many companies have already started the migration to the Cloud and many individuals share their personal informations on social networks. While some of the data are public information, many of them are personal and even quite sensitive. Unfortunately, the current access mode is purely right-based: the provider first authenticates the client, and grants him access, or not, according to his rights in the access-control list. Therefore, the provider itself not only has total access to the data, but also knows which data are accessed, by whom, and how: privacy, which includes secrecy of data (confidentiality), identities (anonymity), and requests (obliviousness), should be enforced. Moreover, while high availability can easily be controlled, and thus any defect can immediately be detected, failures in privacy protection can remain hidden for a long time. The industry of the Cloud introduces a new implicit trust requirement: nobody has any idea at all of where and how his data are stored and manipulated, but everybody should blindly trust the providers. The providers will definitely do their best, but this is not enough. Privacy-compliant procedures cannot be left to the responsibility of the provider: however strong the trustfulness of the provider may be, any system or human vulnerability can be exploited against privacy. This presents too huge a threat to tolerate. The distribution of the data and the secrecy of the actions must be given back to the users. It requires promoting privacy as a global security notion.

In order to protect the data, one needs to encrypt it. Unfortunately, traditional encryption systems are inadequate for most applications involving big, complex data. Recall that in traditional public key encryption, a party encrypts data to a single known user, which lacks the expressiveness needed for more advanced data sharing. In enterprise settings, a party will want to share data with groups of users based on their credentials. Similarly, individuals want to selectively grant access to their personal data on social networks as well as documents and spreadsheets on Google Docs. Moreover, the access policy may even refer to users who do not exist in the system at the time the data is encrypted. Solving this problem requires an entirely new way of encrypting data.

A first natural approach would be fully homomorphic encryption (FHE, see above), but a second one is also Functional Encryption (FE), that is an emerging paradigm for public-key encryption: it enables more fine-grained access control to encrypted data, for instance, the ability to specify a decryption policy in the ciphertext so that only individuals who satisfy the policy can decrypt, or the ability to associate keywords to a secret key so that it can only decrypt documents containing the keyword. Our work on functional encryption centers around two goals:

  1. to obtain more efficient pairings-based functional encryption;
  2. and to realize new functionalities and more expressive functional encryption schemes.

Another approach is secure multi-party computation protocols, where interactivity might provide privacy in a more efficient way, namely for machine learning techniques. Machine learning makes an intensive use of comparisons, for the activation of neurons, and new approaches have been proposed for efficient comparisons with interactive protocols.

4.2 Searchable Encryption

Searchable Encryption (SE) is another technique that aims to protect users' privacy with regard to data uploaded to the cloud. Searchable Encryption is equally concerned with scalability, with the aim to accomodate large real-world databases. As a concrete application, an email provider may wish to store its users’ emails in an encrypted form to provide privacy; but it is obviously highly desirable that users should still be able to search for emails that contain a given word, or whose date falls within a given range. Businesses may also want to outsource databases containing sensitive information, such as client data, for example to dispense with a costly dedicated IT department. To be usable at all, the outsourced encrypted database should still offer some form of search functionality. Failing that, the entire database must be downloaded to process each query to the database, defeating the purpose of cloud storage.

In many contexts, the amount of data outsourced by a client is large, and the overhead incurred by generic solutions such as FHE or FE becomes prohibitive. The goal of Searchable Encryption is to find practical trade-offs between privacy, functionality, and efficiency. Regarding functionality, the focus is mainly on privately searching over encrypted cloud data, altough many SE schemes also support simple forms of update operation. Regarding privacy, SE typically allows the server to learn some information on the encrypted data. This information is formally captured by a leakage function. Security proofs show that the cloud server does not learn any more information about the client's data than what is expressed by the leakage function.

The additional flexibility afforded by allowing a controlled amount of leakage enables SE to offer highly efficient solutions, which can be deployed in practice on large datasets. The main goal of our research in this area is to analyze the precise privacy impact of different leakage functions; propose new techniques to reduce this leakage; as well as extend the range of functionality achieved by Searchable Encryption.

4.3 Post-Quantum Standardization

In recent years, there has been very significant investment on research on quantum computers – machines that exploit quantum mechanical phenomena to solve mathematical problems that are difficult or intractable for conventional computers. If large-scale quantum computers are ever built, they will be able to break many of the public-key cryptosystems currently in use. This would seriously compromise the confidentiality and integrity of digital communications on the Internet and elsewhere. The goal of post-quantum cryptography (also called quantum-resistant cryptography or quantum-safe cryptography) is to develop cryptographic systems that are secure against both quantum and classical computers, and can interoperate with existing communication protocols and networks.

In 2016, NIST initiated a process to solicit, evaluate, and standardize one or more quantum-resistant public-key cryptographic algorithms. The first selection of standards was announced in July 2022. Out of four standards, three are based on lattice problems: CRYSTALS-KYBER for encryption, CRYSTALS-DILITHIUM and FALCON for signature. We intend to study the best lattice algorithms in order to assess the security of the three NIST standards (and two other NIST finalists SABER and NTRU) based on the hardness of lattice problems.

4.4 Provable Security for the Quantum Internet

With several initiatives such as the development of a 2,000 km quantum network in China, the access of IBM's quantum platform freely available and the efforts made in the EU for instance with the quantum internet alliance team, we can assume that in a further future, not only the adversary has potential access to a quantum computer, but everybody may have access to quantum channels, allowing honest parties to exchange quantum data up to a limited amount. Going one step further than post-quantum cryptography, it is therefore needed to carefully study the security models and properties of classical protocols or the soundness of classical theoretical results in such a setting. Some security notions have already been defined but others have to be extended, such as the formal treatment of superposition attacks initiated by Zhandry.

On the positive side, some quantum primitives which are already well-studied, unconditionally quantum secure and already deployed in practice (such as Quantum Key Distribution) allow for new security properties such as everlasting confidentiality for sensitive long-lived data (which holds even if an attacker stores encrypted data now and decrypts them later when a quantum computer becomes available). We intend to study to what extent allowing honest parties to have access to currently available (or near-term) quantum technologies allows to achieve quantum-enhanced protocols (for classical functionalities) with improved security or efficiency beyond what is possible classically.

5 Social and environmental responsibility

5.1 Footprint of research activities

Unfortunately, private computation is usually at a huge cost: it definitely costs more to compute on encrypted data than on clear inputs. However, our goal is definitely to reduce this cost, as it will improve the user experience at the same time, with shorter computation time.

5.2 Impact of research results

Strong privacy for the Cloud would have a huge societal impact since it would revolutionize the trust model: users would be able to make safe use of outsourced storage, namely for personal, financial and medical data, without having to worry about failures or attacks of the server.

Both design of new primitives and study of the best attacks are essential for this goal.

6 New results

All the results of the team have been published (see the list of publications). They are all related to the research program (see Section 3) and the research projects (see Sections 7 and 8):

  • Advanced encryption (registration-based encryption 18)
  • Decentralized multi-client functional encryption (optimal security notions 20, verifiability 21)
  • Quantum-safe constructions (attribute-based encryption 16, PAKE 13, anonymous credentials 15, identity-based signatures 23)
  • Zero-knowledge proofs (proof of shuffling 14, proof of subset-membership 22)
  • Searchable Encryption (cuckoo hashing 11, oblivious RAM 12, forward-security 19)
  • Cryptanalysis (SVP approximation 10)
  • Quantum cryptography (copy-protection 17)

7 Bilateral contracts and grants with industry

7.1 Bilateral contracts with industry

  • PhD CIFRE Worldline
    – Baptiste Cottier (2019–2023) – Privacy-preserving anomaly detection
  • PhD Leanear
    – Lenaïck Gouriou (2019–2023) – Advanced encryption with post-quantum security
  • PhD CIFRE Thales
    – Hugo Senet (2020–2023) – Protocoles cryptographiques pour un anonymat post-quantique
  • PhD CIFRE Cosmian
    – Paola de Perthuis (2020–2023) – Efficient Protocols for Secure Computation over Confidential Data
  • PhD CIFRE Thales
    – Hugo Beguinet (2021–2024) – Chiffrement avancé post-quantique sur les réseaux euclidiens
  • PhD CIFRE CryptoExperts
    – Nicolas Bon (2022–2025) – Design of optimized operations for homomorphic cryptography
    – Guirec Lebrun (2022–2025) – Protocoles cryptographiques d’authentification post-quantique
  • PhD Thales
    – Éric Sageloli (2023–2026) – Sécurité de protocoles et primitives cryptographiques face à un attaquant quantique

7.2 Grants with industry

RESQUE: Résilience Quantique

Participants: Céline Chevalier, Eric Sageloli.

  • Program:
  • Duration:
    September 2023 – August 2026
  • Coordinator:
  • Partners:
    CryptoExperts, CryptoNext, TheGreenBow, ANSSI, CNES, Inria
  • Inria contact:
    Céline Chevalier
  • Summary:
    RESQUE aims at developing cryptographic tools that will resist quantum computers.
SecNISQ: Calcul Securisé Multipartite pour Architectures NISQ

Participants: Céline Chevalier, Paul Hermouet.

  • Program:
  • Duration:
    October 2021 – October 2025
  • Coordinator:
    Elham Kashefi
  • Partners:
    LIP6/Univ. Paris 6, CRED/Univ. Paris 2, VeriQloud, Inria
  • Inria contact:
    Céline Chevalier
  • Summary:
    SecNISQ aims at developing a platform for multi clients-server distributed quantum computing. While currently some quantum devices are remotely accessible, providing integrity as well as privacy of data processing remains a challenging task that we aim to address in this project. We have recently proposed the first framework for secure multi party quantum computing as a novel path to address this challenge. However optimizing these protocols for currently available NISQ devices on one hand as well as specific usecases identified by the industry partner on the other hand, is the main target of this project. This will be based on detailed use-case analyses, classical and quantum sub-protocol designs, guided by numerical simulations of the performances that could be obtained in realistic situation taking into account also the underlying constraints of the NISQ architecture.
Crypto4Graph-AI: advanCed pRivacY Preserving TechnOlogies for enterprise knowledge GRAPHs and Artificial Intelligence

Participants: David Pointcheval, Paola De Perthuis.

  • Program:
  • Duration:
    September 2021 – August 2024
  • Coordinator:
    Fraunhofer / Cosmian
  • Partners:
    Cosmian, Fraunhofer, Eccenca
  • Inria contact:
    David Pointcheval
  • Summary:
    The overall objective of CRYPTO4GRAPH-AI is to develop a data management framework to train machine learning (ML) models that utilize privacy enhancing technologies (PETs) to discover knowledge graphs (KGs) for improved decision making. KGs enjoy increasing popularity in enterprises for their ability to integrate data from heterogeneous sources, plus rich metadata and a machine-comprehensible semantic representation of background knowledge in a uniform structure. Beyond Google’s or Facebook’s graphs, KGs have been applied to enterprise cybersecurity, supply chain management, genomics, drug-drug-interaction, and biological networks. While data owners are often not willing to share sensitive data such as business-critical data, this data can be valuable for analyses in other contexts for different stakeholders or even for multiple data owners interested to mutualise their data.
PRESTO: PRocessing Encrypted Streams for Traffic Oversight

Participants: David Pointcheval, Ngoc Ky Nguyen.

  • Program:
  • Duration:
    January 2020 – June 2024
  • Coordinator:
    David Pointcheval
  • Partners:
    Inria/ENS/Cascade, IMT/Telecom SudParis, LORIA, Orange Labs, 6cure
  • Inria contact:
    David Pointcheval
  • Summary:

    While GDPR (General Data Protection Regulation) imposes some privacy constraints, growing threats against servers require traffic analysis to detect malicious behaviors. This analysis includes identification of illegitimate connections to mitigate denial of service attacks, content filtering to limit content exposition or content leakage, and log management for later forensic analysis. Security Information and Event Management (SIEM) that deals with internal and external threats should still remain effective under GDPR constraints. Data protection usually means encryption, which in turn heavily limits the traffic analysis capabilities.

    The main goal of this project is to bridge the gap between these two security and privacy requirements, with advanced cryptographic tools (such as searchable encryption, functional encryption, fully homomorphic encryption, and multi-party computation) in order to provide privacy to the end-users while allowing traffic monitoring by the network security manager. While current tools already work on encrypted streams by analyzing the meta-data only, advanced encryption tools may enrich the analysis by specific researches in the encrypted payload.

8 Partnerships and cooperations

8.1 European initiatives

8.1.1 H2020 projects

PARQ: Lattices in a Parallel and Quantum World

Participants: Henri Bambury, Wissam Ghantous, Jianwei Li, Phong Nguyen.

  • Program:
    H2020 ERC Advanced Grant
  • Duration:
    From July 1, 2020 to June 30, 2025
  • Partners:
    Inria, CNRS
  • Coordinator:
    Phong Nguyen
  • Summary:
    Today's digital world creates many security and privacy issues. But cryptography, a pillar of cybersecurity, is facing two major challenges. The first challenge is the threat of quantum computers, fueled by massive investment worldwide. Shor showed that a quantum computer can break the most prevalent forms of public-key cryptography used every day by e-commerce and bitcoins. This threat is now taken seriously by governmental organizations: the NIST initiated in 2016 a process to standardize by 2024 public-key cryptographic algorithms resistant to quantum computers. The second challenge is new environments, such as big data, IoT, or crypto-currencies. Because classical cryptography no longer suffices for these applications, novel cryptographic schemes and functionalities have been developed, e.g. to allow anyone to compute with encrypted data. But these benefits come at the cost of security uncertainty: it requires more risky assumptions and makes it more difficult to select parameters with confidence. Worryingly, the past few years have seen several established cryptographic assumptions collapse. Lattices are mathematical objects which have emerged in the past twenty years as the key technique to respond to these challenges: the ongoing standardization of homomorphic encryption and the majority of the candidates to NIST's post-quantum standardization rely on the conjectured hardness of lattice problems. This proposal aims at readying lattice-based cryptography for real-world deployment, by protecting it against the most powerful adversaries, from ASIC farms to quantum computers. We will study the best parallel and quantum algorithms for lattice problems, and derive automated tools to select safe parameters. The proposal will use the renowned expertise of the PI in lattice algorithms and cryptanalysis to explore the quantum frontiers of cryptanalysis.

8.2 National initiatives

QAT: Quantum computing Architectures, Algorithms, Applications and their Theory

Participants: Sami Abdul Sater, Francesco Arzani, Ulysse Chabaud, Jack Davis, Harold Ollivier, Rajarsi Pal, Mathys Rennela.

  • Program:
    Exploratory Action Inria
  • Duration:
    January 2023 – December 2024
  • Inria contact:
    Harold Ollivier
  • Summary:

    Our research group believes that the development of Quantum Information Processing requires a holistic approach that integrates architectures, algorithms, and applications. We recognize that applications are crucial for end-users, but they cannot be achieved without the necessary enablers, which are algorithms and architectures. Moreover, the practical impact of this technology on current and future hardware depends on a constant interplay between these three topics, especially given the limited hardware resources available.

    To this end, our research program is focused on developing advanced theoretical tools that can help us understand the capabilities of quantum computers, improve their design for specific algorithms, and unlock new functionalities using quantum information processing. By taking this integrated approach, we hope to advance the state-of-the-art in Quantum Information Processing and provide valuable insights for future developments.

HQI: Hybrid HPC Quantum Initiative

Participants: Céline Chevalier, Quoc Huy Vu.

  • Program:
    ANR PEPR Quantique
  • Duration:
    April 2022 – April 2028
  • Coordinator:
  • Partners:
    CEA, CNRS, CPU, GENCI, Inria
  • Inria contact:
    Céline Chevalier
  • Summary:
    Following the announcement made in January 2021 of the National Quantum Strategy by the President of the French Republic, the SGPI entrusted the CEA, GENCI and Inria with the responsibility of setting up a national hybrid HPC quantum-computing platform named HQI. The project to set up this platform consists of purchases of quantum computers (entrusted to GENCI and subject to a separate agreement), research and development entrusted to industrialists and academics as well as support for communities using the platform (objects of this agreement).
SecureCompute: Security of Computations

Participants: Florette Martinez, Brice Minaud, Ngoc Ky Nguyen, David Pointcheval, Robert Schaedlich.

  • Program:
    ANR PEPR Cybersécurité
  • Duration:
    July 2022 – June 2028
  • Coordinator:
  • Partners:
    ENS, Inria, CNRS, CEA
  • Coordinator:
    David Pointcheval
  • Summary:
    For cost reasons and the sake of simplification, companies massively outsource their data storage and data processing to untrusted providers. Many individuals do the same with their photos or other personal documents. Although these documents contain sensitive information, they are exposed on the web, and information leaks regularly break the news. Financial, economic, or medical data are at stake, with all the risks that this can bring, both to companies and to individuals. The purpose of this project is to study the cryptographic mechanisms allowing to ensure the security of data, during their transfer, at rest, but also during processing, despite uncontrolled environments such as the Internet for exchanges and the Cloud for hosting and processing. Security, in this context, not only means confidentiality but also integrity, a.k.a. the correct execution of operations. It is indeed essential, when outsourcing data and processing, that no sensitive information can leak but also that the results are correct. There are many areas of application, especially when large amounts of data are involved, such as medical analysis, logs, training data, etc.
SaFED: Safe and Functional Encrypted Databases

Participants: Brice Minaud, Michael Reichle.

  • Program:
  • Duration:
    October 2019 – March 2024
  • Coordinator:
    Brice Minaud
  • Partners:
    DGA, Inria/ENS/Cascade
  • Summary:
    This project addresses the security of encrypted databases, with the proposal of new searchable encryption techniques and deeper security analysis.
CryptiQ: Cryptography in a Quantum World

Participants: Céline Chevalier, Quoc Huy Vu.

  • Program:
  • Duration:
    January 2019 – June 2023
  • Coordinator:
    Céline Chevalier
  • Partners:
    Univ Panthéon-Assas
  • Summary:
    In a context where the threat of a quantum attacker which could completely break many widely-used public-key cryptosystems becomes plausible and quantum communication technologies become available in practice, the goal of the project is to anticipate these major changes in three plausible scenarios (post-quantum cryptography, quantum-enhanced classical cryptography and cryptography in a quantum world), and find in each case the most relevant security models to construct and prove concrete protocols.

9 Dissemination

9.1 Promoting scientific activities

9.1.1 Scientific events: organisation

Member of the steering committees
  • Conferences: CANS (David Pointcheval), PKC (David Pointcheval), Asiacrypt (Phong Nguyen)
  • Franco-Japanese Cooperation in Cybersecurity: Phong Nguyen

9.1.2 Scientific events: selection

Member of the conference program committees
  • CT-RSA ’23 (Brice Minaud)
  • PKC '23 (David Pointcheval)
  • Crypto '23 (David Pointcheval, Brice Minaud)
  • LatinCrypt '23 (Céline Chevalier)

9.1.3 Journal

Member of the editorial boards
  • Journal of Applicable Algebra in Engineering, Communication and Computing (AAECC): David Pointcheval (Associate Editor)
  • Journal of Mathematical Cryptology: Phong Nguyen (Associate Editor)
  • Journal of Cryptology / Topical Collection on Computing on Encrypted Data: David Pointcheval

9.1.4 Books

In the collection SCIENCES – Cryptography, Data Security of ISTE Publishing Knowledge and Wiley:

  • Asymmetric Cryptography: Primitives and Protocols (Edited by David Pointcheval) – ISBN : 9781789450965 – January 2023
  • Symmetric Cryptography 2: Cryptanalysis and Future Directions. Chapter 7. Meet-in-the-Middle Cryptanalysis (Brice Minaud) – ISBN : 9781789451474 – December 2023

9.2 Teaching

  • Introduction to Cryptology (ENS 1st year students): a total of 20 hours of lecture, 20 hours of TA/year
  • Techniques in cryptography and cryptanalysis (Master M2 MPRI): 24 hours of lecture/year
  • Cryptographic protocols: computational and symbolic proofs (Master M2 MPRI): 12 hours of lecture/year
  • Introduction to Cryptography (Master M1, ESI Léonard de Vinci)
  • Public-key cryptography (Master MSSIS, ESIEA)

10 Scientific production

10.1 Major publications

  • 1 articleM.Michel Abdalla, D.Dario Catalano and D.Dario Fiore. Verifiable Random Functions: Relations to Identity-Based Key Encapsulation and New Constructions.Journal of Cryptology2732014, 544-593
  • 2 articleM.Masayuki Abe, G.Georg Fuchsbauer, J.Jens Groth, K.Kristiyan Haralambiev and M.Miyako Ohkubo. Structure-Preserving Signatures and Commitments to Group Elements.Journal of Cryptology2922016, 363--421
  • 3 inproceedingsD.Divesh Aggarwal, J.Jianwei Li, P. Q.Phong Q Nguyen and N.Noah Stephens-Davidowitz. Slide Reduction, Revisited—Filling the Gaps in SVP Approximation.CRYPTO 2020 - 40th Annual International Cryptology ConferenceSanta Barbara / Virtual, United StatesAugust 2020, 274-295HALDOI
  • 4 inproceedingsP.Pyrros Chaidos, V.Véronique Cortier, G.Georg Fuchsbauer and D.David Galindo. BeleniosRF: A Non-interactive Receipt-Free Electronic Voting Scheme.Proceedings of the 23rd ACM Conference on Computer and Communications Security (CCS '16)ACM Press2016, 1614--1625
  • 5 inproceedingsJ.Jérémy Chotard, E.Edouard Dufour Sans, R.Romain Gay, D.David Pointcheval and D. H.Duong Hieu Phan. Decentralized Multi-Client Functional Encryption for Inner Product.ASIACRYPT '18 - 24th Annual International Conference on the Theory and Application of Cryptology and Information SecurityLecture Notes in Computer ScienceAdvances in Cryptology - ASIACRYPT '1811273Brisbane, AustraliaSpringerDecember 2018HALDOI
  • 6 inproceedingsR.Romain Gay, D.Dennis Hofheinz, E.Eike Kiltz and H.Hoeteck Wee. Tightly CCA-Secure Encryption Without Pairings.Advances in Cryptology -- Proceedings of Eurocrypt '16 (2)9665Lecture Notes in Computer ScienceSpringer2016, 1--27
  • 7 inproceedingsS.Sergey Gorbunov, V.Vinod Vaikuntanathan and H.Hoeteck Wee. Predicate Encryption for Circuits from LWE.Advances in Cryptology -- Proceedings of CRYPTO '15 (2)9216Lecture Notes in Computer ScienceSpringer2015, 503-523
  • 8 inproceedingsB.Brice Minaud and M.Michael Reichle. Dynamic Local Searchable Symmetric Encryption.Crypto 2022 - 42nd Annual International Cryptology ConferenceLNCS - 13510Advances in Cryptology – CRYPTO 2022Santa Barbara, United StatesSpringerAugust 2022HALDOI
  • 9 inproceedingsW.Willy Quach, H.Hoeteck Wee and D.Daniel Wichs. Laconic Function Evaluation and Applications.59th Annual IEEE Symposium on Foundations of Computer Science (FOCS 2018)IEEE2018

10.2 Publications of the year

International journals

International peer-reviewed conferences

  • 12 inproceedingsL.Léonard Assouline and B.Brice Minaud. Weighted Oblivious RAM, with Applications to Searchable Symmetric Encryption.EUROCRYPT 2023 - Annual International Conference on the Theory and Applications of Cryptographic TechniquesLNCSLNCS - Lecture Notes in Computer Science14004Lyon, FranceSpringerApril 2023, 426-455HALDOIback to text
  • 13 inproceedingsH.Hugo Beguinet, C.Céline Chevalier, D.David Pointcheval, T.Thomas Ricosset and M.Mélissa Rossi. GeT a CAKE: Generic Transformations from Key Encaspulation Mechanisms to Password Authenticated Key Exchanges.Applied Cryptography and Network Security. ACNS 2023Conference on Applied Cryptography and Network Security (ACNS '23)13906Lecture Notes in Computer ScienceKyoto, JapanSpringer Nature SwitzerlandMay 2023, 516-538HALDOIback to text
  • 14 inproceedingsR.Rohann Bella, X.Xavier Bultel, C.Céline Chevalier, P.Pascal Lafourcade and C.Charles Olivier-Anclin. Practical Construction for Secure Trick-Taking Games Even With Cards Set Aside.FC2023 - Twenty-Seventh International Conference Financial Cryptography and Data SecurityFC2023 - Twenty-Seventh International Conference Financial Cryptography and Data SecurityBol, Brač, Croatia2023HALback to text
  • 15 inproceedingsO.Olivier Blazy, C.Céline Chevalier, G.Guillaume Renaut, T.Thomas Ricosset, É.Éric Sageloli and H.Hugo Senet. Efficient Implementation of a Post-Quantum Anonymous Credential Protocol.ARES '23: Proceedings of the 18th International Conference on Availability, Reliability and SecurityARES 2023: The 18th International Conference on Availability, Reliability and SecurityBenevento, ItalyACMAugust 2023, 1-11HALDOIback to text
  • 16 inproceedingsT.Théophile Brézot, P.Paola de Perthuis and D.David Pointcheval. Covercrypt: an Efficient Early-Abort KEM for Hidden Access Policies with Traceability from the DDH and LWE.ESORICS 2023 - 28th European Symposium on Research in Computer SecurityLa Haye, NetherlandsSeptember 2023HALback to text
  • 17 inproceedingsC.Céline Chevalier, P.Paul Hermouet and Q.-H.Quoc-Huy Vu. Semi-Quantum Copy-Protection and More.TCC 2023Taipei, TaiwanNovember 2023HALback to text
  • 18 inproceedingsD.Dario Fiore, D.Dimitris Kolonelos and P.Paola de Perthuis. Cuckoo Commitments: Registration-Based Encryption and Key-Value Map Commitments for Large Spaces.Asiacrypt 2023 - International Conference on the Theory and Application of Cryptology and Information SecurityCanton, ChinaDecember 2023HALback to text
  • 19 inproceedingsB.Brice Minaud and M.Michael Reichle. Hermes: I/O-Efficient Forward-Secure Searchable Symmetric Encryption.Asiacrypt 2023 - International Conference on the Theory and Application of Cryptology and Information SecurityGuangzhou, ChinaDecember 2023HALback to text
  • 20 inproceedingsK.Ky Nguyen, D. H.Duong Hieu Phan and D.David Pointcheval. Optimal Security Notion for Decentralized Multi-Client Functional Encryption.Applied Cryptography and Network Security. ACNS 202313906Lecture Notes in Computer ScienceKyoto, JapanSpringer Nature SwitzerlandMay 2023, 336-365HALDOIback to text
  • 21 inproceedingsD.Duy Nguyen, D. H.Duong Hieu Phan and D.David Pointcheval. Verifiable Decentralized Multi-Client Functional Encryption for Inner Product.Advances in Cryptology - Proceedings of ASIACRYPT '23Advances in Cryptology - ASIACRYPT 2023Guanzhou, ChinaDecember 2023HALback to text
  • 22 inproceedingsD.David Pointcheval. Linearly-Homomorphic Signatures for Short Randomizable Proofs of Subset Membership.Eighth International Joint Conference on Electronic Voting (E-Vote-ID '23)Luxembourg, LuxembourgOctober 2023HALback to text
  • 23 inproceedingsÉ.Éric Sageloli, P.Pierre Pébereau, P.Pierrick Méaux and C.Céline Chevalier. Shorter and Faster Identity-Based Signatures with Tight Security in the (Q)ROM from Lattices.Lecture Notes in Computer Science21st International Conference on Applied Cryptography and Network Security13905Kyoto, JapanSpringerJune 2023, 634--663HALDOIback to text

Doctoral dissertations and habilitation theses

  • 24 thesisL.Léonard Assouline. Computing with private information: Techniques from Cryptology.PSL University; Ecole normale supérieureDecember 2023HAL
  • 25 thesisB.Baptiste Cottier. Contribution to interactive cryptography.Ecole Normale Superieure de Paris - ENS ParisJanuary 2023HAL
  • 26 thesisL.Lénaïck Gouriou. Delegation and Tracing for Attribute-Based Cryptography.ENS UlmMay 2023HAL
  • 27 thesisM.Michael Reichle. Constructions of Advanced Cryptographic Primitives.Ecole normale supérieure - ENS PARISOctober 2023HAL
  • 28 thesisH.Hugo Senet. Anonymity and Secrecy Preserving Post-Quantum Cryptographic Protocols.École normale supérieureSeptember 2023HAL
  • 29 thesisQ.-H.Quoc-Huy Vu. Facing and Exploiting the Quantum Wave in Computing: New Security Definitions and Cryptographic Constructions.Université Paris - Panthéon - AssasFebruary 2023HAL