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  • Publication . 2021
    English
    Authors: 
    Baelde, David; Delaune, Stéphanie; Koutsos, Adrien; Moreau, Solène;
    Publisher: HAL CCSD
    Country: France
    Project: EC | POPSTAR (714955)

    International audience; Bana and Comon have proposed a logical approach to proving protocols in the computational model, which they call the Computationally Complete Symbolic Attacker (CCSA). The proof assistant Squirrel implements a verification technique that elaborates on this approach, building on a meta-logic over the CCSA base logic. In this paper, we show that this meta-logic can naturally be extended to handle protocols with mutable states (key updates, counters, etc.) and we extend \Squirrel's proof system to be able to express the complex proof arguments that are sometimes required for these protocols. Our theoretical contributions have been implemented in Squirrel and validated on a number of case studies, including a proof of the YubiKey and YubiHSM protocols.

  • English
    Authors: 
    Kadija Charni; Nathalie Greenan; Janna Besamusca;
    Publisher: HAL CCSD
    Country: France
    Project: EC | InGRID-2 (730998)

    In this report, we explore the feasibility of a European database of working conditions clauses in collective agreements in EU countries. Our proposal builds on the methodology developed by the University of Amsterdam (UvA) and the WageIndicator Foundation to build an international database of collective agreements and in the BARCOM (VS/2016/0106) and COLBAR Europe (VS/2019/0077) projects to collect and code European collective agreements. It also builds on the CNAM-CEET CAGE project which has developed a research infrastructure in France to study the outcomes of negotiations on gender professional equality and employer behaviour. The idea is to combine structured information from an employer-level survey with coded information from a database of collective agreements and unstructured data from an archive recording the full content of the OCR processed texts of collective agreements. Such an infrastructure would allow better analysis of the bargaining process, bargaining outcomes and employer behaviour. Using the example of gender equality clauses, we demonstrate the feasibility of building such an infrastructure and the added value of using coded information and text mining methods for comparative analysis. Two European surveys, the ECS and ESES, can be combined with the database of collective agreements at individual and/or sectoral level. We explore how collective agreements at sector and company level should be collected to achieve some form of representativity.; Dans ce rapport, nous explorons la faisabilité d'une base de données européenne relative aux clauses concernant les conditions de travail dans les conventions collectives des pays de l'UE. Notre proposition s'appuie sur la méthodologie développée par l'Université d'Amsterdam (UvA) et la Fondation WageIndicator pour construire une base de données internationale de conventions collectives et dans les projets BARCOM (VS/2016/0106) et COLBAR Europe (VS/2019/0077) pour collecter et coder les conventions collectives européennes. Il s'appuie également sur le projet CAGE du CNAM-CEET qui a développé une infrastructure de recherche en France pour étudier les résultats des négociations sur l'égalité professionnelle femmes-hommes et le comportement des employeurs. L'idée est de combiner des informations structurées provenant d'une enquête auprès des employeurs avec des informations codées provenant d'une base de données de conventions collectives et des données non structurées provenant d'une archive enregistrant le contenu intégral des textes océrisé des conventions collectives. Une telle infrastructure permettrait une meilleure analyse du processus de négociation, des résultats de la négociation et du comportement des employeurs. En utilisant l'exemple des clauses d'égalité professionelle femmes-hommes, nous démontrons la faisabilité de la construction d'une telle infrastructure et la valeur ajoutée de l'utilisation des informations codées et des méthodes d'exploration de texte pour l'analyse comparative. Deux enquêtes européennes, l'ECS et l'ESES, peuvent être combinées avec la base de données des conventions collectives au niveau individuel et/ou sectoriel. Nous étudions comment les conventions collectives au niveau du secteur et de l'entreprise devraient être collectées pour atteindre une certaine forme de représentativité.

  • Publication . Part of book or chapter of book . Conference object . Article . Report . 2021
    Open Access
    Authors: 
    Julien Bensmail; Foivos Fioravantes; Fionn Mc Inerney; Nicolas Nisse;
    Publisher: Springer International Publishing
    Country: France
    Project: EC | SYSTEMATICGRAPH (725978)

    International audience; This paper introduces the largest connected subgraph game played on an undirected graph G. In each round, Alice first colours an uncoloured vertex of G red, and then, Bob colours an uncoloured vertex of G blue, with all vertices initially uncoloured. Once all the vertices are coloured, Alice (Bob, resp.) wins if there is a red (blue, resp.) connected subgraph whose order is greater than the order of any blue (red, resp.) connected subgraph. We first prove that, if Alice plays optimally, then Bob can never win, and define a large class of graphs (called reflection graphs) in which the game is a draw. We then show that determining the outcome of the game is PSPACE-complete, even in bipartite graphs of small diameter, and that recognising reflection graphs is GI-hard. We also prove that the game is a draw in paths if and only if the path is of even order or has at least 11 vertices, and that Alice wins in cycles if and only if the cycle is of odd length. Lastly, we give an algorithm to determine the outcome of the game in cographs in linear time.

  • French
    Authors: 
    Gautron, Joël; Réhault-Godbert, Sophie;
    Publisher: HAL CCSD
    Country: France
    Project: EC | PPILOW (816172)
  • Publication . Report . Project deliverable . Preprint . 2021
    Open Access
    Authors: 
    Eisl, Andreas; Rubio, Eulalia;
    Publisher: Zenodo
    Country: France
    Project: EC | EU IDEA (822622), EC | EU IDEA (822622)

    So far, most research on differentiated integration has focused either on its causes or on its broader consequences for the process of European integration. In contrast, in this paper we apply a public policy approach. Through an analysis of the functioning of various differentiated governance arrangements that exist in the EU economic policy field (particularly governing the EMU, the EU energy sector and the access of third countries into the Single Market) we aim to understand under which conditions differentiated procedures and institutions prove to be effective in attaining the stated objectives and in adjusting to changing circumstances while minimising undesirable effects. Doing so, we make two contributions to the existing scholarship. First, we develop an encompassing and dynamic definition of policy effectiveness that allows us to assess and compare the performance of economic differentiated integration arrangements. Second, we identify a number of institutional factors that positively influence the effectiveness of EU differentiated economic policy arrangements. These include (1) institutional set-ups tailor-made to the policy objectives of the differentiated organisation, (2) unified, simple and clear governance frameworks, (3) adaptable and flexible institutional designs and (4) institutional provisions to include nonparticipating and third countries. The theoretical framework presented in this paper to study the conditions under which differentiated integration is effective may inspire the research agenda on differentiated integration also beyond the economic policy field.

  • French
    Authors: 
    Bernet, Nicolas; Bozonnet, Sophie; Daboussi, Fayza; de Berardinis, Véronique; Faulon, Jean-Loup; Garcia-Bernet, Diana; Gras, Gabriel; Legrand, Jack; Ouarné, Francoise; Li-Beisson, Yonghua; +9 more
    Publisher: HAL CCSD
    Country: France
    Project: EC | PREP-IBISBA (871118), EC | IBISBA 1.0 (730976)
  • English
    Authors: 
    Nair, Sreeja,; Meirim, Filipe; Pereira, Mário; Ferreira, Carla; Shapiro, Marc;
    Publisher: HAL CCSD
    Country: France
    Project: EC | LightKone (732505)

    The tree is an essential data structure in many applications. In a distributed application, such as a distributed file system, the tree is replicated.To improve performance and availability, different clients should be able to update their replicas concurrently and without coordination. Such concurrent updates converge if the effects commute, but nonetheless, concurrent moves can lead to incorrect states and even data loss. Such a severe issue cannot be ignored; ultimately, only one of the conflicting moves may be allowed to take effect. However, as it is rare, a solution should be lightweight. Previous approaches would require preventative cross-replica coordination, or totally order move operations after-the-fact, requiring roll-back and compensation operations. In this paper, we present a novel replicated tree that supports coordination-free concurrent atomic moves, and provably maintains the tree invariant. Our analysis identifies cases where concurrent moves are inherently safe, and we devise a lightweight, coordination-free, rollback-free algorithm for the remaining cases, such that a maximal safe subset of moves takes effect. We present a detailed analysis of the concurrency issues with trees, justifying our replicated tree data structure. We provide mechanized proof that the data structure is convergent and maintains the tree invariant. Finally, we compare the response time and availability of our design against the literature.; L’arbre est une structure de données essentielle. Quand l’application est distribuée, par exemple dans un système de fichiers distribué, l’arbre est répliqué. Pour améliorer les performances et la disponibilité, les différents clients doivent pouvoir mettre à jour leurs répliques simultanément et sans coordination. Celles-ci convergent si les mises à jour commutent entre elles ; néanmoins, même dans ce cas, des opérations “move” concurrentes peuvent conduire à des états incorrects, et même à la perte de données. Au bout du compte, entre deux opérations “move” en conflit, seule l’une des deux peut être autorisée à prendre effet. Cependant, comme ce cas est rare, la solution doit être légère. Les approches précédentes nécessitaient une coordination préventive des répliques, ou des retours en arrière a posteriori. Dans cet article, nous présentons un nouvel arbre répliqué, qui met en œuvre une opération “move” atomique sans coordination, et dont nous prouvons qu’il maintient l’invariant d’arbre.Notre analyse identifie les cas où les “move” concurrents sont intrinsèquement sûrs, et proposons un algorithme léger, sans coordination et sans retour-arrière, pour les autres cas, de sorte qu’un sous-ensemble maximal et sûr de “move” prenne effet. Nous présentons une analyse détaillée des problèmes de cohérence dans les arbres. Nous fournissons une preuve mécanisée que la structure des données est convergente et maintientl’invariant d’arbre. Enfin, nous comparons le temps de réponse et la disponibilité de notre concept à la littérature.

  • Publication . Conference object . Article . Report . 2021
    Open Access English
    Authors: 
    Charlie Jacomme; Steve Kremer;
    Publisher: HAL CCSD
    Country: France
    Project: EC | SPOOC (645865)

    Passwords are still the most widespread means for authenticating users, even though they have been shown to create huge security problems. This motivated the use of additional authentication mechanisms in so-called multi-factor authentication protocols. In this article, we define a detailed threat model for this kind of protocol: While in classical protocol analysis attackers control the communication network, we take into account that many communications are performed over TLS channels, that computers may be infected by different kinds of malware, that attackers could perform phishing, and that humans may omit some actions. We formalize this model in the applied pi calculus and perform an extensive analysis and comparison of several widely used protocols—variants of Google 2-step and FIDO’s U2F (Yubico’s Security Key token). The analysis is completely automated, generating systematically all combinations of threat scenarios for each of the protocols and using the P ROVERIF tool for automated protocol analysis. To validate our model and attacks, we demonstrate their feasibility in practice, even though our experiments are run in a laboratory environment. Our analysis highlights weaknesses and strengths of the different protocols. It allows us to suggest several small modifications of the existing protocols that are easy to implement, as well as an extension of Google 2-step that improves security in several threat scenarios.

  • Open Access English
    Authors: 
    Maryl, Maciej; Błaszczyńska, Marta; Zalotyńska, Agnieszka; Taylor, Laurence; Avanço, Karla; Balula, Ana; Buchner, Anna; Caliman, Lorena; Clivaz, Claire; Costa, Carlos; +21 more
    Publisher: HAL CCSD
    Countries: France, Croatia, Croatia
    Project: EC | OPERAS-P (871069), EC | OPERAS-P (871069)

    This report discusses the scholarly communication issues in Social Sciences and Humanities that are relevant to the future development and functioning of OPERAS. The outcomes collected here can be divided into two groups of innovations regarding 1) the operation of OPERAS, and 2) its activities. The “operational” issues include the ways in which an innovative research infrastructure should be governed (Chapter 1) as well as the business models for open access publications in Social Sciences and Humanities (Chapter 2). The other group of issues is dedicated to strategic areas where OPERAS and its services may play an instrumental role in providing, enabling, or unlocking innovation: FAIR data (Chapter 3), bibliodiversity and multilingualism in scholarly communication (Chapter 4), the future of scholarly writing (Chapter 5), and quality assessment (Chapter 6). Each chapter provides an overview of the main findings and challenges with emphasis on recommendations for OPERAS and other stakeholders like e-infrastructures, publishers, SSH researchers, research performing organisations, policy makers, and funders. Links to data and further publications stemming from work concerning particular tasks are located at the end of each chapter.

  • English
    Authors: 
    Ivaldi, Serena; Maurice, Pauline; Gomes, Waldez; Theurel, Jean; Wioland, Liên; Atain-Kouadio, Jean-Jacques; Claudon, Laurent; Hani, Hind; Kimmoun, Antoine; Sellal, Jean-Marc; +5 more
    Publisher: HAL CCSD
    Country: France
    Project: EC | An.Dy (731540)
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