In the harsh environment where n ode density is sparse, the slow-moving nodes cannot effectively utilize the encountering opportunities to realize the self-organized identity authentications, and do not have the chance to join the network routing. However, considering m ost of the communications in opportunistic networks are caused by forwarding operations, there is no need to establish the complete mutual authentications for each conversation. Accordingly, a novel trust management scheme is presented based on the information of behavior feedback, in order to complement the insufficiency of identity authentications. By utilizing the certificate chains based on social attributes, the mobile nodes build the local certificate graphs gradually to realize the web of "Identity Trust" relationship. Meanwhile, the successors generate Verified Feedback Packets for each positive behavior, and consequently the "Behavior Trust" relationship is formed for slow-moving nodes. Simulation result shows that, by implementing our trust scheme, the d elivery probability and trust reconstruction ratio can be effectively improved when there are large numbers of compromised nodes, and it means that our trust management scheme can efficiently explore and filter the trust nodes for secure forwarding in opportunistic networks.
Since web services intended for the same application environment tend to be functionally homogeneous, researchers have turned to their non-functional aspects in order to constructively compare web services and choose an appropriate one. In general, quality of service is very important to users. Many schemes that consider quality assessment have been proposed for web service selection. With the increasing number of qualityrelated attributes, an effective quality assessment method needs satisfactory scalability. Schemes based on the analytic hierarchy process(AHP) meet this requirement. However, prevalent methods in this vein overlook the fact that the traditional AHP needs a complete judgment matrix. In practice, all the information needed to construct a judgment matrix is often unavailable for a variety of reasons, due to which certain judgments cannot be made. In this paper, for an incomplete judgment matrix, we propose an improved AHP approach to consistency verification and the subsequent ordering. Our method can deal with situations where information is insufficient,and inherits all the merits of the traditional AHP approach. A case study establishes the effectiveness of our proposed method.
