CAT: A Context-Aware Trust Model for Open and Dynamic Systems

The requirements for spontaneous interactions in open and dynamic systems create security issues and necessitate the incorporation of trust management into each software entity to make decisions. Trust encompasses various quality attributes (e.g., security, competence, honesty) and helps in making appropriate decisions. In this paper, we present CAT, an interaction-based Context-Aware Trust model for open and dynamic systems by considering services as contexts. We identify a number of trust proper-ties including context and risk awareness and address those in the proposed model. A context-similarity parameter is proposed to make decisions in similar situations. A time-based ageing parameter is introduced to change trust values over time without any further interaction. We present direct and indirect recommendations and apply path-based ageing on indirect recommendations. A mechanism to calculate the accuracy of recommendations is described. This accuracy is used to differentiate between reliable and unreliable recommendations in the total trust calculation.