aachen.de

Emerging digital environments and infrastructures, such as distributed security services and distributed computing ser-vices, have generated new options of communication, infor-mation sharing, and resource utilization in past years. How-ever, when distributed services are used, the question arises of to what extent we can trust service providers to not violate security requirements, whether in isolation or jointly. An-swering this question is crucial for designing trustworthy dis-tributed systems and selecting trustworthy service providers. This paper presents a novel trust measurement method for distributed systems, and makes use of propositional logic and probability theory. The results of the qualitative part include the specification of a formal trust language and the representation of its terms by means of propositional logic formulas. Based on these formulas, the quantitative part re-turns trust metrics for the determination of trustworthiness with which given distributed systems are assumed to fulfill a particular security requirement. 1