Covered Trust Values in Distributed Systems

During the last years it has become recognized that trust is an essential component in the design of protocols in distributed systems If for example a Key Distribution Center KDC is employed to distribute public keys the receiver of such a key has to trust the KDC that the key is authentic Sometimes a trusted entity may recommend another entity as being trustworthy which in turn can recommend further entities Obviously the longer such a trust path grows the smaller the trust towards the nal entity will be On the other hand the higher the number of trustworthy recommendations about an entity the more trustworthy this entity will become These observations have led to the introduction of trust values When deriving the value of a trust path from the trust values of the individual entities in a distributed manner one faces the problem that the estimation of each other s trust worthiness is a private matter Up to now this problem has been circumvented by either ignoring it or by not allowing for the derivation of a trust path s value In this paper we propose a technique for the derivation of the value of a trust path without exposing the individual trust values to other entities