A trust model for ubiquitous systems based on vectors of trust values

Ubiquitous computing foresees a massively networked world supporting a population of diverse but cooperating mobile devices where trust relationships between entities are uncertain. Though there have been lots of effort focusing on trust for ubiquitous systems, they did not attach enough importance to uncertainty in their model. On the other hand, most of the works draw a general picture without a detailed computational model. In this paper, we present a trust model based on the vectors of trust values of different entities. The evaluation of trust depends upon the recommendation of peer entities common to the interacting entities. These recommendations are weighted according to the number and time of past interactions. Furthermore we present a method of handling false recommendations without introducing significant computational burden. The model can calculate trust between two entities in situations both in which there is past experience among the interacting entities and in which the two entities are communicating for the first time. Several tuning parameters are suggested which can be adjusted to meet the security requirement of a ubiquitous system.