What is Trust Evaluation

The significance of efficient security mechanisms in P2P and Grid systems is unquestionable, since security is considered to be a quality of service factor for such systems. Traditional security mechanisms in P2P and Grid systems include encryption, sand-boxing and other access control and authentication mechanisms. Unfortunately these techniques incur additional overhead. By using trust and reputation-based mechanisms, the additional overhead is minimized. The deployment of efficient trust mechanisms results to a safer communication between P2P or Grid nodes, increasing the quality of service and making P2P and Grid technology more appealing. The aim of this book chapter is to lay the theoretical background of concepts such as trust, reputation, trust graphs and trust functions. Furthermore it presents classification schemes for trust functions, discussing the characteristics and differences of each classification. Finally, it analyses popular trust and reputation-based management mechanisms that have been implemented in both P2P and Grid systems.