Event-B based invariant checking of secrecy in group key protocols

Abstract—The correctness of group key protocols in commu-nication systems remains a great challenge because of dynamic characteristics of group key construction as we deal with an open number of group members. In this paper, we propose a solution to model group key protocols and to verify their required properties, in particular secrecy property, using the event-B method. Event-B deals with tools allowing invariant checking, and can be used to verify group key secrecy property. We define a well-formed formal link between the group protocol model and the event-B counterpart model. Our approach is applied on a tree-based group Diffie-Hellman protocol that dynamically outputs group keys using the logical structure of a balanced binary tree. I

A Formal Development Method of Control Systems using Event B Approach

This paper presents a formal method for the development of control systems. We aim at developing a program controlling the operative part of a control system. We first build an abstract model of the operative part and complete this model to get a model of the control system. The elements introduced to change the abstract model of the operative part to the automated system forms the controller. The next steps consists in refining the abstract model to get a model of the operative part capturing every important feature. The method is developped through a case study : a parcel sorting system

Formal Verification of Secrecy in Group Key Protocols Using Event-B

Group key security protocols play an important role in today’s communication systems. Their verification, however, remains a great challenge because of the dynamic characteristics of group key construction and distribution protocols. Security properties that are well defined in normal two-party protocols have different meanings and different interpretations in group key distribution protocols, specifically, secrecy properties, such as group secrecy, forward secrecy, backward secrecy, and key independence. In this paper, we present a method to verify forward secrecy properties for group-oriented protocols. The method is based on a correct semantical link between group key protocols and event-B models and also uses the refinement process in the B method to model and verify group and forward secrecy. We use an event-B first-order theorem proving system to provide invariant checking for these secrecy properties. We illustrate our approach on the Tree based Group Diffie-Hellman protocol as case study

Transformation of B Specifications into UML Class Diagrams and State Machines

We propose a rule-based approach for transforming B abstract machines into UML diagrams. We believe that important insight into the structure underlying a B model can be gained by representing it in UML, for example in order to explain the model to stakeholders that are not experts in the B formalism. We focus on the generation of class diagram and state machines. Our approach does not prescribe a mechanic algorithm for translation, giving the modeler choices to adapt the resulting UML models as appropriate

Formal Development Method of Automated Systems using the Temporal Logic of Actions TLA

International audienceThe paper presents a method for control systems formal development. We focus on the refinement process used for the development of a control part controlling an operative part of an automated (controlled) system satisfying requirements. We first build an abstract model of both operative and control parts and complete this model to get a model of the automated system. The next steps consists in refining the control part and the operative one to get a model of the automated system capturing every important feature. The method is developed through a case study : a parcel sorting system. We use the temporal logic of actions TLA+ which deals with refiement and proved usufull for the specification and the verifiation of safety and liveness properties

A Specification and Validation Technique Based on STATEMATE and FNLOG

The original publication is available at http://www.springerlink.comInternational audienceThe paper presents a specification technique borrowing features from an formal and a semi-formal methods each in order to cover all features needed in the development of real-time and critical systems. The work is a contribution to the integration of formal and semi-formal methodsn namely STATEMATE and the temporal logic FNLOG [7]. FNLOG deals with quantitative temporal properties and is compatible with STATEMATE. The proposed integration approach uses the notations of STATEMATE and FNLOG, defines a various transformations rules of a STATEMATE specification towards FNLOG and extends the axiomatic of the temporal logic FNLOG by new lemmas to deal with duration properties. The paper presents the various steps of our integration approach

Comparative Study of the Long-Term Impact of the COVID-19 Pandemic on Mental Health and Nutritional Practices Among International Elite and Sub-Elite Athletes: A Sample of 1420 Participants from 14 Countries

Background Although several studies have shown that the Coronavirus Disease 2019 (COVID-19) lockdown has had negative impacts on mental health and eating behaviors among the general population and athletes, few studies have examined the long-term effects on elite and sub-elite athletes. The present study aimed to investigate the long-term impact of COVID-19 lockdown on mental health and eating behaviors in elite versus sub-elite athletes two years into the pandemic. A cross-sectional comparative study was conducted between March and April 2022, involving athletes from 14 countries, using a convenient non-probabilistic and snowball sampling method. A total of 1420 athletes (24.5 ± 7.9 years old, 569 elites, 35% women, and 851 sub-elites, 45% women) completed an online survey-based questionnaire. The questionnaire included a sociodemographic survey, information about the COVID-19 pandemic, the Depression, Anxiety and Stress Scale—21 Items (DASS-21) for mental health assessment, and the Rapid Eating Assessment for Participants (REAP-S) for assessing eating behavior. Results The results showed that compared to sub-elite athletes, elite athletes had lower scores on the DASS-21 (p = .001) and its subscales of depression (p = .003), anxiety (p = .007), and stress (p < .001), as well as a lower REAP-S score indicating lower diet quality (p = .013). Conclusion In conclusion, two years into the pandemic, elite athletes were likelier to have better mental health profiles than sub-elite athletes but surprisingly had lower diet quality. Key Points Elite athletes had better mental health profiles compared to sub-elite athletes, with lower levels of depression, anxiety, and stress. Elite athletes reported greater psychological support and perceived themselves as more financially secure during the pandemic than sub-elite athletes do. Elite athletes were more likely to have poor eating habits compared to sub-elite athletes

Une approche formelle pour la spécification et la vérification des systèmes temps-réel

Texte intégral accessible uniquement aux membres de l'Université de LorraineOur aim is the use of formal techniques for the development of control-command system, which constitutes the program component of real-time systems. Generally, using a formal method for program development first consists in formally specifying the expected behaviour of the target program and then in proving that the program implementation satisfies this specification. We can adopt this strategy in real-time systems and develop the control-command program by means of specifying its behaviour. Nevertheless, it seems more natural to proceed otherwise. In fact, a real-time system or an automated system is constituted by one" imposed" operative part, which acts on its environment, and a control program (automation system) piloting the physical system. The system, whose behaviour interests the user, is the automated one and not the automation one, which is the task of the developer. The automated system aots on an environment which itself may be assumed as a system i.e. the target system. It is defined by abstraction. The user objective is then to have an automated system satisfying target system requirements. However, the challenge for the developer is to design a suitable development methodology for this end. In a first part of this thesis, we propose a development methodology for the specification and the verification of automation system, given the automated system and operative part descriptions. We exhibit different behaviour properties of these systems, which needs the prediction of system's behaviour in the future, given the observed behaviour ending at a certain point. In this context, we extend temporal logic with new operators and propose a new language called IPTL for reasoning about such properties, defining the relationship between system behaviour in the future and its history. We illustrate our approach through industrial examples and prove that the specification and verification processes.Notre but est d'utiliser des techniques formelles pour le développement de systèmes d'automatisation (système de contrôle-commande) formant le composant logiciel d'un système temps-réel. Succinctement, utiliser une méthode formelle pour le développement d'un logiciel consiste à spécifier de façon formelle le comportement attendu du logiciel sous forme de propriétés, et à prouver que le logiciel lui-même satisfait cette spécification. Une spécification exprime les besoins de l'utilisateur et sert aussi de référence au développeur. Dans le cas des applications temps-réel, le système dont le comportement intéresse l'utilisateur est le système automatisé formé d'une partie physique qui existe et d'un système d'automatisation qu'on cherche à développer. L'utilisateur souhaite que le système automatisé agisse sur un environnement (système cible) de façon que ce dernier se comporte selon ses souhaits. Étant donné qu'un système temps-réel contient des composants physiques préexistants, il nous est apparu que son développement doit se faire de façon différente que pour les logiciels classiques. Dans ce mémoire, nous proposons d'abord une méthodologie de développement qui consiste à construire et valider une spécification formelle du système d'automatisation, compte tenu de la description du système automatisé et de la partie opérationnelle. Nous montrons que le cadre méthodologique s'adapte à différents cas de systèmes temps-réel. Nous examinions ensuite nos besoins de spécification pour les différents composants d'un système temps-réel qui nécessitent de pouvoir exprimer l'évolution prévisible en fonction d'un comportement observé jusqu'à un certain point. Ceci nous amène à compléter les opérateurs de la logique temporelle classique par de nouveaux opérateurs et à proposer un nouveau langage de spécification dénommé LTPI, conçu comme une extension de la logique temporelle, et qui permet de décrire une partie du comportement d'un système comme une conséquence d'une autre partie qui l'a précédée. Nous illustrons notre approche à travers quelques exemples de cas industriels, et nous prouvons que le processus de spécification et de vérification se simplifie en utilisant le formalisme proposé

Utilisation conjointe de B et TLA+ pour la modélisation et la vérification des systèmes réactifs

conjointement à l'Ecole d'Eté Temps Réel 2005 - ETR 2005National audienceLa méthode B fournit un cadre rigoureux de développement de systèmes mais sa limitation concerne le type des propriétés exprimées car seuls les invariants sont considérés. Notre travail a pour objectif d'utiliser le B événementiel pour exprimer des propriétés temporelles de fatalité et d'équité. La logique temporelle des actions TLA+ a prouvé son efficacité dans l'expression et la vérification de propriétés d'équité. Elle se base sur le concept de raffinement, d'action et de transition qui exprime une compatibilité avec une modélisation B événementiel. Notre contribution consiste à proposer une méthode de spécification et de vérification utilisant conjointement B et TLA+ et leur outils de vérification l'AtelierB et le prouveur de théorèmes Isabelle