Hmm-based trust model

Abstract. Probabilistic trust has been adopted as an approach to taking security sensitive decisions in modern global computing environments. Existing proba-bilistic trust frameworks either assume fixed behaviour for the principals or in-corporate the notion of ‘decay ’ as an ad hoc approach to cope with their dynamic behaviour. Using Hidden Markov Models (HMMs) for both modelling and ap-proximating the behaviours of principals, we introduce the HMM-based trust model as a new approach to evaluating trust in systems exhibiting dynamic be-haviour. This model avoids the fixed behaviour assumption which is considered the major limitation of existing Beta trust model. We show the consistency of the HMM-based trust model and contrast it against the well known Beta trust model with the decay principle in terms of the estimation precision.