Assurer l'appropriation des données personnelles et l'interopérabilité des applications Web sociaux décentralisées est actuellement un sujet controversé, surtout en prenant compte des aspects de la vie privée et du contrôle d'accès. Il est important d'améliorer le Web social de telle manière à permettre des modèles d'affaires viables tout en étant capable de fournir une plus grande appropriation des données et l'interopérabilité des données par rappport à la situation actuelle. A cet égard, nous avons concentré notre recherche sur trois thèmes différents: le contrôle d'identité, l'authentifiaction et le contrôle d'accès. Tout d'abord, nous abordons le sujet de l'identité décentralisée en proposant un nouveau standard Web appelé "Web Identity and Discovery" (WebID), qui offre un mécanisme d'identification simple et universel qui est distribué et ouvertement extensible. Ensuite, nous passons à la question de l'authentification où nous proposons WebID-TLS, un protocole d'authentification décentralisé qui permet l'authentification sécurisée, simple et efficace sur le Web en permettant aux personnes de se connecter à l'aide de certificats clients. Nous étendons également WebID-TLS, en offrant des moyens d'effectuer de l'authentification déléguée et de la délégation d'accès. Enfin, nous présentons notre dernière contribution, un service de contrôle d'accès social, qui sert à protéger l'accès aux ressources Linked Data générés par les utilisateurs (par exemple, les données de profil, messages du mur, conversations, etc) par l'application de deux mesures: la "distance de proximité sociale" et "contexte social" / Ensuring personal data ownership and interoperability for decentralized social Web applications is currently a debated topic, especially when taking into consideration the aspects of privacy and access control. Since the user's data are such an important asset of the current business models for most social Websites, companies have no incentive to share data among each other or to offer users real ownership of their own data in terms of control and transparency of data usage. We have concluded therefore that it is important to improve the social Web in such a way that it allows for viable business models while still being able to provide increased data ownership and data interoperability compared to the current situation. To this regard, we have focused our research on three different topics: identity, authentication and access control. First, we tackle the subject of decentralized identity by proposing a new Web standard called "Web Identity and Discovery" (WebID), which offers a simple and universal identification mechanism that is distributed and openly extensible. Next, we move to the topic of authentication where we propose WebID-TLS, a decentralized authentication protocol that enables secure, efficient and user friendly authentication on the Web by allowing people to login using client certificates and without relying on Certification Authorities. We also extend the WebID-TLS protocol, offering delegated authentication and access delegation. Finally we present our last contribution, the Social Access Control Service, which serves to protect the privacy of Linked Data resources generated by users (e.g. pro le data, wall posts, conversations, etc.) by applying two social metrics: the "social proximity distance" and "social contexts"

Ensuring personal data ownership and interoperability for decentralized social Web applications is currently a debated topic, especially when taking into consideration the aspects of privacy and access control. Since the user's data are such an important asset of the current business models for most social Websites, companies have no incentive to share data among each other or to offer users real ownership of their own data in terms of control and transparency of data usage. We have concluded therefore that it is important to improve the social Web in such a way that it allows for viable business models while still being able to provide increased data ownership and data interoperability compared to the current situation. To this regard, we have focused our research on three different topics: identity, authentication and access control. First, we tackle the subject of decentralized identity by proposing a new Web standard called "Web Identity and Discovery" (WebID), which offers a simple and universal identification mechanism that is distributed and openly extensible. Next, we move to the topic of authentication where we propose WebID-TLS, a decentralized authentication protocol that enables secure, efficient and user friendly authentication on the Web by allowing people to login using client certificates and without relying on Certification Authorities. We also extend the WebID-TLS protocol, offering delegated authentication and access delegation. Finally we present our last contribution, the Social Access Control Service, which serves to protect the privacy of Linked Data resources generated by users (e.g. pro le data, wall posts, conversations, etc.) by applying two social metrics: the "social proximity distance" and "social contexts"