This book presents the design and development of an access control architecture for the Internet of Things (IoT) systems. It considers the significant authentication and authorization issues for large-scale IoT systems, in particular, the need for access control, identity management, delegation of access rights and the provision of trust within such systems. It introduces a policy-based access control approach for the IoT that provides fine-grained access for authorized users to services while protecting valuable resources from unauthorized access. Further, the book discusses an identity-less, asynchronous and decentralized delegation model for the IoT leveraging the advantage of blockchain technology. It also presents an approach of attribute-based identity and examines the notion of trust in an IoT context by considering the uncertainty that exists in such systems. Fully explaining all the techniques used, the book is of interest to engineers, researchers and scientists working in the field of the wireless sensor networks, IoT systems and their access control management.