Hysteresis-based robust trust computing mechanism for cloud computing

Cloud computing has been the new paradigm in distributed systems where users can access computing resources and pay only for usage similar to other utilities like electricity, water, gas and telephony. Service Level Agreements signed at the beginning between the clients and service providers stipulate conditions of the services including the QoS requirements. Trust can be used to quantify the QoS levels of providers and rank them according to their performances. Hence trust management systems can play an important role in identifying the right service provider who would maintain the QoS at the levels required by the clients. Researchers have proposed several trust computing mechanisms based on different techniques and trust metrics on the literature. Almost all of these mechanisms increment or decrement the trust scores monotonously based on the inputs. This is a major vulnerability that can be exploited by adversaries to force the trust scores towards extreme values. In this paper, the authors propose a novel trust computing mechanism based on hysteresis function which requires extra efforts to force the output from one end to the other. Hysteresis functions are immune to small changes and hence can be used to protect the system from sporadic attacks. The proposed mechanism has been tested using simulations. The test results show that the trust scores computed using the proposed mechanism are more robust and stable in the face of attacks than other mechanisms.