The Internet of Things (IoT) is a network that integrates a variety of heterogeneous nodes, such as connected devices (sensors, robots, smart phones ...), connected cars, smart homes, etc. These smart objects communicate and collaborate in distributed and dynamic environments that are facing several security challenges. Trust management is one of the most important challenges in IoT. Existing trust management solutions do not meet the new requirements of IoT such as heterogeneity, mobility and scalability. In this work, we proposed a hierarchical and scalable blockchain-based trust management protocol with mobility support in massively distributed IoT systems. In our protocol, mobile smart objects disseminate trust information on service providers to the blockchain. Thus, all the objects will have a global view on each service provider in the architecture, which speeds up the trust evaluation process. In addition, our protocol is resilient against the most known malicious attacks such as bad-mouthing, ballot-stuffing and cooperative attacks. We confirm the efficiency of our proposal through theoretical analysis and extensive simulations. Finally, we show that it outperforms existing solutions especially in terms of scalability, mobility support, communication and computation costs.

The Internet of things (IoT) is a new technology that aims to connect billions of physical devices to the Internet. The components of IoT communicate and collaborate between each other in distributed and dynamic environments, which are facing several security challenges. In addition, the huge number of connected objects and the limitation of their resources make the security in IoT very difficult to achieve. In this thesis, we focus on the application of lightweight cryptographic approaches and blockchain technology to address security problems in IoT, namely : authentication and trust management. First, we were interested on some kind of IoT applications where we need to control remotely the execution of smart actuators using IoT devices. To solve this problem, we proposed an efficient and fine-grained access control solution, based on the Attribute Based Encryption (ABE) mechanism and oneway hash chains. Using formal security tools, we demonstrated the security of our scheme against malicious attacks. Second, we tackled the problem of authentication in IoT based fog computing environments. Existing authentication techniques do not consider latency constraints introduced in the context of fog computing architecture. In addition, some of them do not provide mutual authentication between devices and fog servers. To overcome these challenges, we proposed a novel, efficient and lightweight mutual authentication scheme based on blockchain technology and secret sharing technique. We demonstrated the efficiency of our authentication scheme through extensive simulations. The third problem treated in this work is the trust management in IoT. Existing trust management protocols do not meet the new requirements introduced in IoT such as heterogeneity, mobility and scalability. To address these challenges, we proposed a new scalable trust management protocol based on consortium blockchain technology and fog computing paradigm, with mobility support. Our solution allows IoT devices to accurately assess and share trust recommendations about other devices in a scalable way without referring to any pre-trusted entity. We confirmed the efficiency of our proposal through theoretical analysis and extensive simulations. Finally, we showed that our protocol outperforms existing solutions especially in terms of scalability, mobility support, communication and computation.