The Research On Models And Methods Of Trust Evaluation

With the rapid development of the distributed network, new requirements are put forward to security management technology. Trust is a research focusing on present network security field which provides flexible safety measurement mechanism through the measurement and evaluation of trust information wrapped in network peers. As the base for trust evaluation mechanism, trust evaluation model studies how to assess and sort peers' reliability, however, construction of a highly precise trust evaluation model with low load is still challenging work due to the complexity and uncertainty of trust. This paper discusses theories and critical technologies of trust evaluation model from four perspectives including trust relationship described by trust cloud, distributed implementation of global trust, trust evaluation based on resource attribute and trust evaluation and resource management based on grid QoS, and presents some new trust evaluation models and methods. The purpose of our work is to provide supporting technologies for the popularization of trust mechanism in distributed networks.With regard to the rationality problem of existing trust evaluation models, we first carry out in-depth research on the cloud theory and come up with the concept of trust cloud. By using trust cloud to pick and describe subjective trust information, we describe in a unified manner the randomness and fuzziness in trust relation as well as their correlation. Algorithm of cloud similarity measurement is presented and decision-making through trust cloud on service security is also realized.Then based on further study of global trust mechanism, we present a global trust model in P2P environment through mathematic analysis and distributed implementation method. This paper provides two distributed implementation methods and experiment them with different types of malice peers described before. The experimental results are used as the basis for evaluating different network environment that the two methods can be applied. With the same resource requirements, resource management prefers to choose the highest reputation peer obtained by global trust models, which causes overload imbalance and failure of new peers serving the system. A novel resource scheduling algorithm based on the probability of peer reputation is proposed. It is shown via simulation that the algorithm achieves better performance on keeping overload balance and resisting attack of malice peers. At the same time, the new peers also obtain opportunity to serve the system.While most subjective trust models focus on entity-centered issues such as reputation, they do not model the content, ie the nature and use of the information being exchanged. Due to this problem, existing trust models fail to promise the trust computation of some special domains. According to the transferable property of trust relation, the paper proposes a novel fine-grained trust model which is based on resource attributes. Compared with prior trust models, the proposed model increases trust evaluation object. This paper simulates some use case scenarios and describes a simulation environment. Simulations show that compared with similar exising trust models, the proposed model is more accurate on trust evaluation and more reasonable and scalable on model architecture.At present, trust model in grid environment focuses on transaction experience while omitting the evaluation of peers' proper property. This situation indicates that the trust information between peers cannot be sufficiently collected and the trust evaluate result is not precise. Moreover, existing models cannot make full use of grid computing fundamental architecture, and trust mechanism and resource management mechanism are isolated. Addressing above problems and those in present grid QoS research work, This paper presents a novel trust evaluation and resource scheduling model GRDM-Q. This model evaluates trust on the basis of resources' QoS and uses the evaluation results as the most important factor for selecting resource, which realizes the integration of trust mechanism and resource management mechanism. Experments show that the new model is an effective approach to evaluate trust and manage resource in grid environment.