Internet of Things (IoT) is an emerging computational paradigm based on the cooperation among physical objects connected by infrastructure networks, with the goal of providing users and objects themselves with new advanced and ubiquitous services. Such a perspective leads us into a new era rich of opportunities, thanks to the possibility for the users of interacting with a lot of future smart and digital environments like houses, offices, transports, health services, in almost all the aspects of our lives.

To implement these attractive expectations, a great amount of data is required to be mutually exchanged among all the IoT actors -- i.e. users and interconnected objects -- and this is a fundamental characteristic of IoT which requires adequate measures for assuring the security of the systems and processes as well as the privacy of individuals and data. 
Obviously, increasing the level of confidence and acceptance in IoT becomes a priority if we target at its widest diffusion. This is an exciting and not trivial challenge to address into IoT domain, particularly in presence of sensitive infrastructures and strategic services. Indeed, it is necessary to provide privacy and security by harmonizing different and conflicting constraints. On one hand, in fact, it is necessary to face the presence of a potentially wide number of interconnected objects, often provided of autonomous intelligence, to serve with scalable and flexible tools capable of ensuring data safety and reliable processes; on the other hand, we need to spread autonomy in recognizing threats and activing protections, but without affecting the efficiency of the system with complex and heavy procedures.

An attractive solution, widely applied and investigated by researchers in different contexts, is represented by trust- and reputation-based systems. Also in an IoT scenario such systems represent a promising solution that can play a fundamental role for realizing safe environments even though the specificity of such environments often require to develop new trust and reputation mechanisms.