Trust transfer in distributed systems

Abstract

Trust transfer is a common technique employed in trust management systems to establish relationships between parties that are strangers. It is also well known that trust is not always transferable. That is, given an existing trust relationship, it may or may not be possible to derive new trust from it. In particular, it is not known under which constraints trust is transferable. In this paper we investigate trust transfer and identify when trust is transferable. Our analysis starts with a simple trust model. By using the model, we find that trust transfer is related to trust policy entailment. We then present a modal logic system which captures how trust and beliefs evolve in distributed systems. With the modal logic system we identify the key constraints on trust transfer regarding the communication between the trustor and the recommender and the trustor's belief state. © 2007 International Federation for Information Processing.