Kouadio Rodrigue N'GORAN Thesis Defense

Today's society is characterized by a highly mobile population and growing needs in terms of sharing large volumes of sensitive data within companies and collaborating with partner or competitor organizations. These collaborations bring many benefits to companies in terms of scalability and economic growth. However, the IT systems of these organizations are exposed to various types of increasingly sophisticated threats and cyberattacks. Traditional perimeter-based infrastructure security strategies are no longer sufficient. The Zero Trust security model is a cybersecurity approach that considers all entities in an infrastructure as potentially vulnerable at all times and everywhere. This strategy is positioned as a response to the problem of securing these heterogeneous, complex, dynamic, and distributed systems. However, its implementation varies according to the system context, and requires organizational and cultural changes. Indeed, collaborative systems are characterized by the need to guarantee the autonomy of the entities involved, the trust between them and the need to protect sensitive information of various kinds exchanged.In this thesis, we propose a Zero Trust security strategy in the context of collaboration between organizations within a community cloud. The model presents a hierarchical architecture for securing exchanges within and between organizations. It provides a decentralized management system for user and organizational identities using decentralized identifiers and verifiable credentials. This method exposes a means of continuous authentication of entities and storage of data in a blockchain-type distributed ledger. Furthermore, the approach offers a technique for assessing trust between organizations. The strategy also includes a mechanism for specifying access policy rules and monitoring collaboration contracts. Experiments have been carried out to prove the effectiveness and reliability of the proposed mechanisms, providing an architecture and associated security measures for deploying a Zero Trust strategy in a collaborative environment.