As the demands of the handheld devices and pervasive services are increasing, the issues of security have alarmingly risen. One can wonder about the pervasive services to be free of every security flaw. The paper suggests a mechanism for a trust based ad-hoc authentication with a distributed trust based mechanism and defined security policies related to access control for pervasive devices. The openness of a true pervasive environment has been encountered with the interaction history and recommendations. The architecture is designed to provide secure autonomous services for an assumed pervasive based scenario. The nature of pervasiveness is satisfied by allowing the novel user to proceed in the system but with the minimum trust initially, which changes dynamically depending on the actions which the user performs. It secures the privacy of the user by the implementation of security policies in the security manager(SM) in order to gain final access to the service.