Conformément aux principes de Linked Data, les fournisseurs de données ont publié des milliards de faits en tant que données RDF. Exécuter les requêtes SPARQL sur les endpoints SPARQL ou les serveurs Triple Pattern Fragments (TPF) permet de consommer facilement des données du Linked Data. Cependant, le traitement des requêtes SPARQL fédérées, tout comme le traitement des requêtes TPF, décompose la requête initiale en de nombreuses sous-requêtes. Les fournisseurs de données ne voient alors que les sous-requêtes et la requête initiale n’est connue que des utilisateurs finaux. La connaissance des requêtes exécutées est fondamentale pour les fournisseurs, afin d’assurer un contrôle de l’utilisation des données, d’optimiser le coût des réponses aux requêtes, de justifier un retour sur investissements, d’améliorer l’expérience utilisateur ou de créer des modèles commerciaux à partir de tendances d’utilisation. Dans cette thèse, nous nous concentrons sur l’analyse des logs d’exécution des serveurs TPF et des endpoints SPARQL pour extraire les Basic Graph Patterns (BGP) des requêtes SPARQL exécutées. Le principal défi pour l’extraction des BGPs est l’exécution simultanée des requêtes SPARQL. Nous proposons deux algorithmes : LIFT et FETA. Sous certaines conditions, nous constatons que LIFT et FETA sont capables d’extraire des BGPs avec une bonne précision et un bon rappel. / Following the principles of Linked Data, data providers published billions of facts as RDF data. Executing SPARQL queries over SPARQL endpoints or Triple Pattern Fragments (TPF) servers allow to easily consume Linked Data. However, federated SPARQL query processing and TPF query processing decompose the initial query into subqueries. Consequently, the data providers only see subqueries and the initial query is only known by end users. Knowing executed SPARQL queries is fundamental for data providers, to ensure usage control, to optimize costs of query answering, to justify return of investment, to improve the user experience or to create business models of usage trends. In this thesis, we focus on analyzing execution logs of TPF servers and SPARQL endpoints to extract Basic Graph Patterns (BGP) of executed SPARQL queries. The main challenge to extract BGPs is the concurrent execution of SPARQL queries. We propose two algorithms: LIFT and FETA. LIFT extracts BGPs of executed queries from a single TPF server log. FETA extracts BGPs of federated queries from a log of a set of SPARQL endpoints. For experiments, we run LIFT and FETA on synthetic logs and real logs. LIFT and FETA are able to extract BGPs with good precision and recall under certain conditions.

Information protection is a key issue for the acceptance and adoption of pervasive computing systems where various portable devices such as smart phones, Personal Digital Assistants (PDAs) and laptop computers are being used to share information and to access digital resources via wireless connection to the Internet. Because these are resources constrained devices and highly mobile, changes in the environmental context or device context can affect the security of the system a great deal. A proper security mechanism must be put in place which is able to cope with changing environmental and system context. Usage CONtrol (UCON) model is the latest major enhancement of the traditional access control models which enables mutability of subject and object attributes, and continuity of control on usage of resources. In UCON, access permission decision is based on three factors: authorisations, obligations and conditions. While authorisations and obligations are requirements that must be fulfilled by the subject and the object, conditions are subject and object independent requirements that must be satisfied by the environment. As a consequence, access permission may be revoked (and the access stopped) as a result of changes in the environment regardless of whether the authorisations and obligations requirements are met. This constitutes a major shortcoming of the UCON model in pervasive computing systems which constantly strive to adapt to environmental changes so as to minimise disruptions to the user. We propose a Context-Aware and Adaptive Usage Control (CA-UCON) model which extends the traditional UCON model to enable adaptation to environmental changes in the aim of preserving continuity of access. Indeed, when the authorisation and obligations requirements are fulfilled by the subject and object, and the conditions requirements fail due to changes in the environmental or the system context, our proposed model CA-UCON triggers specific actions in order to adapt to the new situation, so as to ensure continuity of usage. We then propose an architecture of CA-UCON model, presenting its various components. In this model, we integrated the adaptation decision with usage decision architecture, the comprehensive definition of each components and reveals the functions performed by each components in the architecture are presented. We also propose a novel computational model of our CA-UCON architecture. This model is formally specified as a finite state machine. It demonstrates how the access request of the subject is handled in CA-UCON model, including detail with regards to revoking of access and actions undertaken due to context changes. The extension of the original UCON architecture can be understood from this model. The formal specification of the CA-UCON is presented utilising the Calculus of Context-aware Ambients (CCA). This mathematical notation is considered suitable for modelling mobile and context-aware systems and has been preferred over alternatives for the following reasons: (i) Mobility and Context awareness are primitive constructs in CCA; (ii) A system's properties can be formally analysed; (iii) Most importantly, CCA specifications are executable allowing early validation of system properties and accelerated development of prototypes. For evaluation of CA-UCON model, a real-world case study of a ubiquitous learning (u-learning) system is selected. We propose a CA-UCON model for the u-learning system. This model is then formalised in CCA and the resultant specification is executed and analysed using an execution environment of CCA. Finally, we investigate the enforcement approaches for CA-UCON model. We present the CA-UCON reference monitor architecture with its components. We then proceed to demonstrate three types of enforcement architectures of the CA-UCON model: centralised architecture, distributed architecture and hybrid architecture. These are discussed in detail, including the analysis of their merits and drawbacks.

With the advent of agile programming, lightweight software processes are being favoured over the highly formalised approaches of the 80s and 90s, where the emphasis is on "people, not processes". Likewise, access control may benefit from a less prescriptive approach and an increasing reliance on users to behave ethically. These ideals correlate with optimistic access controls. However, such controls alone may not be adequate as they are retrospective rather proactive. Optimistic access controls may benefit from the stricter enforcement offered by usage control. The latter enables finer-grained control over the usage of digital objects than do traditional access control policies and models, as trust management concerns are also taken into consideration. This thesis investigates the possibility of enhancing optimistic access controls with usage control to ensure that users conduct themselves in a trustworthy manner. Since this kind of approach towards access control has limited applicability, the present study investigates contextualising this approach within a mixed-initiative access control framework. A mixed-initiative access control framework involves combining a minimum of two access control models where the request to information is mediated by a mixture of access policy enforcement agents. In order for this type of integration to be successful, a software development approach was considered that allows for the seamless augmentation of traditional access control with optimistic access control enhanced with usage control, namely the aspect-oriented approach. The aspect-oriented paradigm can facilitate the implementation of additional security features to legacy systems without modifying existing code. This study therefore evaluates the aspect-oriented approach in terms of implementing security concerns. It is evidently difficult to implement access control and in dynamic environments preconfigured access control policies may often change dramatically, depending on the context. In unpredicted circumstances, users who are denied access could often have prevented a catastrophe had they been allowed access. The costs of implementing and maintaining complex preconfigured access control policies sometimes far outweigh the benefits. Optimistic controls are retrospective and allow users to exceed their normal privileges. However, if a user accesses information unethically, the consequences could be disastrous. Therefore it is proposed that optimistic access control be enhanced with some form of usage control, which may prevent the user from engaging in risky behaviour. An initiative towards including security in the earlier phases of the software life cycle is gaining momentum, as it is much easier to design with security from the onset than to use the penetrate-and-patch approach. Unfortunately, incorporating security into software development takes time and developers tend to focus more on the features of the software application. The aspect-oriented paradigm can facilitate the implementation of additional security features in legacy systems without modifying existing code. The current study evaluates the aspect-oriented approach towards enhancing optimistic access control with usage control. The efficacy of the aspect-oriented paradigm has been well established within several areas of software security, as aspect-orientation facilitates the abstraction of these security-related tasks so as to reduce code complexity. / Thesis (PHD)--University of Pretoria, 2010. / Computer Science / unrestricted

No description available.

Organisations such as governments and healthcare bodies are increasingly responsible for managing large amounts of personal information, and the increasing complexity of modern information systems is causing growing concerns about the protection of these assets from insider threats. Insider threats are very difficult to handle, because the insiders have direct access to information and are trusted by their organisations. The nature of insider privacy breaches varies with the organisation’s acceptable usage policy and the attributes of an insider. However, the level of risk that insiders pose depends on insider breach scenarios including their access patterns and contextual information, such as timing of access. Protection from insider threats is a newly emerging research area, and thus, only few approaches are available that systemise the continuous monitoring of dynamic insider usage characteristics and adaptation depending on the level of risk. The aim of this research is to develop a formal framework for an adaptive early warning and response system for insider privacy breaches within dynamic software systems. This framework will allow the specification of multiple policies at different risk levels, depending on event patterns, timing constraints, and the enforcement of adaptive response actions, to interrupt insider activity. Our framework is based on Usage Control (UCON), a comprehensive model that controls previous, ongoing, and subsequent resource usage. We extend UCON to include interrupt policy decisions, in which multiple policy decisions can be expressed at different risk levels. In particular, interrupt policy decisions can be dynamically adapted upon the occurrence of an event or over time. We propose a computational model that represents the concurrent behaviour of an adaptive early warning and response system in the form of statechart. In addition, we propose a Privacy Breach Specification Language (PBSL) based on this computational model, in which event patterns, timing constraints, and the triggered early warning level are expressed in the form of policy rules. The main features of PBSL are its expressiveness, simplicity, practicality, and formal semantics. The formal semantics of the PBSL, together with a model of the mechanisms enforcing the policies, is given in an operational style. Enforcement mechanisms, which are defined by the outcomes of the policy rules, influence the system state by mutually interacting between the policy rules and the system behaviour. We demonstrate the use of this PBSL with a case study from the e-government domain that includes some real-world insider breach scenarios. The formal framework utilises a tool that supports the animation of the enforcement and policy models. This tool also supports the model checking used to formally verify the safety and progress properties of the system over the policy and the enforcement specifications.

Nous vivons une véritable explosion du volume des données personnelles numériques qui sont générés dans le monde chaque jour (ex. capteurs, web, réseaux sociaux, etc.). En conséquence, les particuliers se sentent exposés tandis qu'ils partagent et publient leurs données. Ainsi, il est clair que des outils et des méthodes sont nécessaires pour contrôler la façon dont leurs données sont collectées, gérées et partagées. Les défis sont principalement axées sur le manque d'applications ou de solutions techniques qui assurent la gestion et le partage sécurisés de données personnelles. Le défi principal est de fournir un outil sécurisé et adaptable qui peut être utilisé par tout utilisateur, sans formation technique. Cette thèse fait trois contributions importantes dans le domaine de la protection de la vie privée : (i) Une implémentation du model UCONABC, un modèle de contrôle d'usage, appliqué à un scénario de réseau social, (ii) une extension algébrique de UCON pour contrôler des partages complexes de données (en transformant des données personnelles en données partageable et/ou publiables), et (iii) la conception, l'implémentation et le déploiement sur le terrain d'une plateforme pour la gestion de données sensibles collectées au travers de formulaires d'enquêtes. / We are recently experiencing an unprecedented explosion of available personal data from sensors, web, social networks, etc. and so people feel exposed while they share and publish their data. There is a clear need for tools and methods to control how their data is collected managed and shared. The challenges are mainly focused on the lack of either applications or technical solutions that provide security on how to collect, manage and share personal data. The main challenge is to provide a secure and adaptable tool that can be used by any user, without technical background. This thesis makes three important contributions to the field of privacy: (i) a prototype implementation of the UCONABC model, a usage control model, applied to an online social networks scenario, (ii) an algebraic extension to UCON to control the complex sharing of data (by transforming personal data into sharable and publishable data) and (iii) the design, implementation and field testing of a secure platform to manage sensitive data collected through online forms.

The main focus of this thesis is applied research targeting industrial applications of Usage Control (UCON) and policy-based governance. Nonetheless, we also tackle an associated core problem to address the diverse requirements of the targeted application domains. The core research problem is three-fold. (1) UCON enacts usage control in a fixed life cycle of three temporal phases: pre, ongoing and post. However, emerging security paradigms require custom and finer-grained lifecycles with phases and transitions tailored for the application domain. For example, data hub applications entail data-oriented usage control throughout the different stages of the data lifecycle (e.g., collection, retention, processing and destruction). Therefore, policy systems must enable custom lifecycles to accommodate a wide variety of applications. (2) Although UCON allows attribute values to change and updates usage decisions accordingly, it does not specify a mechanism to govern attribute values. This becomes necessary in decentralised environments where attributes are collected from external parties that are not necessarily trusted. For this reason, policy systems must incorporate a mechanism to govern attributes, prepare them for policy evaluation and ensure their trustworthiness. (3) Due to its widespread adoption, UCON has been extended and adapted for diverse purposes, leading to a proliferation of frameworks. While these variations added significant contributions in their respective fields, they lack comprehensiveness and generality. Therefore, a unified solution is needed to encompass the existing variations of UCON as well as future applications. By addressing these core problems, we aim to leverage policy-based governance in the following four industrial applications: (1) Industrial/International Data Spaces (IDS), (2) data hubs, (3) smart vehicles, and (4) credential transformation.To address these challenges and fulfil our applied research goals, we present six contributions in this thesis. (1) We propose UCON+: an extensible model that extends beyond traditional access and usage control providing a comprehensive framework for policy-based governance. UCON+ builds on the same foundations of UCON, making it an attribute-based model that incorporates continuous monitoring and policy re-evaluation. However, it only defines general structures and common functions, and outlines extensible behaviour to be implemented by concrete extensions. Specifically, UCON+ allows concrete extensions to govern attribute values and updates, and to specify custom lifecycles tailored for their respective requirements. (2) We introduce a general-purpose policy engine that implements the UCON+ model. The engine conserves an Attribute-Based Access Control (ABAC) baseline using a standard policy language. The policy engine also introduces another type of policies used to govern attribute values, and to define and drive custom lifecycles. Thus, different extensions of UCON+ can be realised within the same policy engine using policies, eliminating the need for reimplementation. The policy engine leverages a modular architecture with an optimised implementation. (3) We demonstrate the use of the policy engine in a cloud service that provides an IDS for contract-based data exchange. We specifically used the policy engine and designed a custom lifecycle to govern and drive the contract negotiation between the data provider and data consumer using policies. We also used the policy engine to govern data usage based on the negotiated data sharing agreement. (4) We also showcase the policy engine in a data hub setting, where we leveraged it to track and govern data objects throughout their lifecycles. We designed a lifecycle that captures the different stages of the data lifecycle based on the General Data Protection Regulation (GDPR). We show how data usage is controlled at each stage of the lifecycle using policies. (5) We present a dynamic identity management and usage control framework for smart vehicles using the policy engine. We specifically introduce a policy-based Security Token Service (STS) that issues contextualised capabilities that specify what subjects are allowed to do within the vehicle. The STS also manages the capabilities throughout their lifecycles and revokes them if the corresponding policies are violated, while also taking safety measures into consideration. (6) Finally, we describe an application of the policy engine for policy-based credential transformation. Specifically, we introduce a policy-based credential bridge that exchanges, aggregates or maps credentials between different domains or regulatory frameworks. The bridge uses policies that specify how to transform or issue credentials according to the requirements of each domain.

De nos jours, les technologies de l'information offrent aux utilisateurs la possibilité de travailler avec n'importe qui, à n'importe quel moment, de n'importe où et avec plusieurs dispositifs hétérogènes. Cette évolution favorise un nouveau modèle distribué de collaboration de confiance où les utilisateurs peuvent travailler sur des documents partagés avec qui ils ont confiance. La collaboration multi-synchrone est largement utilisée pour soutenir le travail collaboratif en maintenant des flux simultanés de l'activité des utilisateurs qui divergent et convergent continuellement. Cependant, ce modèle n'offre pas de support concernant l'expression et la vérification de restriction d'usage des données. Cette thèse présente C-PPC, un modèle de collaboration basé sur les contrats et sur la confiance. Dans ce modèle, des contrats sont utilisés comme des règles d'utilisation des données et les utilisateurs collaborent en fonction des niveaux de confiance qu'ils attribuent aux autres en accord avec le respect des contrats. Nous formalisons les contrats en utilisant des concepts déontiques: permission, obligation et prohibition. Les contrats sont inclus dans les historiques d'opérations des données partagées. Le modèle C-PPC fournit un mécanisme pour la fusion des modifications des données et des contrats. N'importe quel utilisateur peut auditer les historiques à n'importe quel moment et les résultats de l'audit sont utilisés pour actualiser les niveaux de confiance en se basant sur une métrique de confiance. Nous proposons une solution reposant sur des authentificateurs basés sur les chaînes de hachage pour garantir l'intégrité des historiques et la responsabilité des utilisateurs. Nous fournissons des algorithmes pour construire les authentificateurs et vérifier les historiques puis nous prouvons leur correction. Des résultats expérimentaux montrent la faisabilité du modèle C-PPC / Nowadays, information technologies provide users ability to work with anyone, at any time, from everywhere and with several heterogeneous devices. This evolution fosters a new distributed trustworthy collaboration model where users can work on shared documents with whom they trust. Multi-synchronous collaboration is widely used for supporting collaborative work by maintaining simultaneous streams of user activities which continually diverge and converge. However, this model lacks support on how usage restrictions on data can be expressed and checked within the model. This thesis proposes "C-PPC", a multi-synchronous contract-based and trust-aware collaboration model. In this model, contracts are used as usage rules and users collaborate according to trust levels they have on others computed according to contract compliance. We formalize contracts by using deontic concepts: permission, obligation and prohibition. Contracts are enclosed in logs of operations over shared data. The C-PPC model provides a mechanism for merging data changes and contracts. Any user can audit logs at any time and auditing results are used to update user trust levels based on a trust metric. We propose a solution relying on hash-chain based authenticators that ensures integrity of logs and user accountability. We provide algorithms for constructing authenticators and verifying logs and prove their correctness. A set of experimental results shows the feasibility of the C-PPC model

L'intelligence ambiante est considérée comme l'une des évolutions majeures de l'informatique ubiquitaire. Elle vise la mise en œuvre des environnements ambiants ou des espaces intelligents permettant d'améliorer la vie quotidienne des utilisateurs, leur bien-être et leur sécurité. Un environnement ambiant dispose d'une multitude d'équipements (capteurs, actionneurs), fournissant des services ubiquitaires atomiques qui sont distribués et de nature hétérogène. Ces services atomiques disponibles dans ce type d'environnement, ne répondent pas directement ou complètement à toutes les exigences et les besoins des utilisateurs. Par ailleurs, ces services de haut niveau peuvent impliquer l'interaction de services ubiquitaires appartenant et/ou contrôlés par différentes structures ou domaines (i.e. environnement multi-domaine). Dans ces travaux de thèse, on a étudié les problématiques reliées à l'agrégation des services ubiquitaires atomiques dans des coopérations et des compositions dans un environnement ambiant multi-domaine afin de répondre à des besoins utilisateurs. Cette étude concerne l'interopérabilité sémantique et comportementale des compositions de services ainsi que leurs spécifications dans un modèle formel basé sur la logique constructive BCDL0. Cette thèse a contribuée par la réalisation d'un canevas sémantique permettant la conception et la vérification formelles des processus coopératifs dans l'assistant à la preuve Isabelle/HOL. Le canevas sémantique proposé consiste en une ontologie de coopération extensible et un langage de spécification de services fiable (Sound) ainsi que des modules de mise en correspondance vers des infrastructures cibles / Ambient Intelligence is considered as the major application domain of ubiquitous computing. It aims at implementing intelligent environments to improve the daily activities, the well-being and the safety of users. An ambient environment has a multitude of devices (sensors, actuators), providing atomic ubiquitous services which are distributed and heterogeneous. These atomic services available in these environments, do not directly or fully meet all the requirements and the needs of users. Moreover, these high-level services may involve the interaction of ubiquitous services owned and/or controlled by different structures or domains (i.e. multi-domain environment). In this work, we studied the problems related to the aggregation of atomic ubiquitous services in cooperations and compositions in an ambient multi-domain environment in order to meet users' needs. This study concerns the semantic and behavioral interoperability of high-level composite services and their formal specification. This latter, is based on the Basic Constructive Description Logic, namely, BCDL0 formal model. This work contributes by realizing a semantic framework for the design and formal verification of cooperative processes in the interactive theorem prover Isabelle/HOL. The proposed semantic framework consists of an extensible cooperation ontology, a sound formal specification language of ubiquitous services and a components for mapping the formally proved cooperatives processes to the targeted infrastructures

Dans le domaine de “smart cities” ou “villes connectées”, les technologies de l’information et de la communication sont intégrées aux services traditionnels de la ville (eau, électricité, gaz, transports collectifs, équipements publics, bâtiments, etc.) pour améliorer la qualité des services urbains ou encore pour réduire les coûts. Les données dans la ville connectée sont généralement produites par une grande variété d’acteurs. Ces données devraient être partagées entre diverses applications ou services. Or, il y a un problème, comment les acteurs peuvent-ils exercer un contrôle sur la façon dont leurs données vont être utilisées? C’est important car pour encourager le partage des données, nous devons établir des relations de confiance entre acteurs. Les acteurs ont confiance s’ils ont la capacité à contrôler l’utilisation de leurs données. Nous prendrons en compte les obligations définies par les acteurs pour leurs données : (i) Abstraction de certaines informations, (ii) Granularité spatio-temporelle, (iii) Classification des acteurs et des objectifs, et (iv) Monétisation des données. Mes contributions sont: (i) Un modèle de contrôle d’utilisation des données. Ce modèle répond aux obligations définies par les acteurs pour leur données. (ii) Une plateforme en tant que service. La plateforme a rajouté des composants nécessaire pour permettre la transparence et la traçabilité d’utilisation des données basée sur le modèle. (iii) Un outil de visualisation. C’est l’implémentation d’un prototype pour que les acteurs puissent exercer un contrôle sur la façon dont leurs données vont être utilisées. (iv) Une évaluation de la performance et l’impact de notre solution. Ces solutions permettent l’établissement des relations de confiance pour le partage des données de Smart Cities basées sur le modèle de contrôle d’utilisation des données. Les résultats de ma thèse peuvent être appliqués à la plateforme IoT Datavenue d’Orange / In smart cities, Information and Communication Technologies, in particular Internet of Things (IoT) Technologies, are integrated into traditional services of our city, for example waste management, air pollution monitoring, and parking to improve quality while reducing costs of these services. IoT data in this context are generated by different actors, such as service providers, developers, and municipal authorities. These data should be shared among applications or services. However, in traditional scenario, there is no sharing of IoT data between them. Each actor consumes data from sensors deployed on behalf of that actor, and network infrastructure maybe shared. In order to encourage IoT data sharing, we need to establish the confidence between the actors. Exercising control over the usage of data by other actors is critical in building trust. Thus, the actors should have an ability to exercise control on how their data are going to be used. This major issue have not been treated in IoT namely Usage Control. In this thesis, we take into account obligations defined by the actors for their data (i) Abstraction of certain information, (ii) Spatial and temporal granularity, (iii) Classification of actors and purposes, and (iv) Monetization of data. For example, requirements of data usage in Intelligent parking applications are (i) Data owners have full access to all the details, (ii) Municipal authorities can access the average occupancy of parking place per street on an hourly basis, (iii) Commercial service providers can access only statistical data over a zone and a weekly basis, and (iv) Monetization of data can be based on subscription types or users roles. Thesis contributions include: (i) Policy-based Data Usage Control Model (DUPO) responds to the obligations defined by actors to their data. (ii) Trustworthy Data Sharing Platform as a Service allows transparency and traceability of data usage with open APIs based on the DUPO and Semantic technologies. (iii) Visualization Tool Prototype enables actors to exercise control on how their data will be used. (iv) Evaluation of the performance and the impact of our solution. The results show that the performance of the added trust is not affecting of the system. Mistrust might hamper public acceptance of IoT data sharing in smart cities. Our solution is key which will establish the trust between data owners and consumers by taking into account the obligations of the data owners. It is useful for data operators who would like to provide an open data platform with efficient enablers to partners, data-based services to clients, and ability to attract partners to share data on their platforms