Abstract: Due to the nature of the WSN and the extreme resource constraints of sensor devices, providing secure, efficient and user-friendly trust initialization is a challenging task. This study identify a coordination communication model which characterizes trust groups in order to promote safe interactions in the ubiquitous environment. Through the proposed TRSCM (Trust and Reputation System for Communication Management), a group of sensor devices that have no pre-shared secrets, establish initial trust by generating various shared secret keys out of an unauthenticated channel. The dynamics of trust group creation, evolution and termination are described, in terms of the history of interactions of the device and on the ontology used to encode the context of trust. After the reasoning the security of the proposed protocols, we implement the middleware on a network testbed and report performance evaluation results.