Research On Trust Models And Access Control Models In Grid Environment

Grid is regarded as the next generation of Internet. In the distributed, heterogeneous and open grid environment, users often have to face unfamiliar partners. As a result, the risk of the lRss RI users' interests will Ee greatly increaseG Tra(?)tiRnal cRmputer security mainly IRcuses on the intrusion prevention from the outer of systems. eowever, traditional security machnisms did not deal with these threats from the inner of systems, which are also major attacks in grid systems. The internal threats of grid systems are mainly brought by malicious behavious. Therefore, it is necessary for grid systems to pre(?)ct anG evaluate users' EehaviRrs. Trust models and reputation systems, which can reflect the credibility of users through monitoring and describing the change of user behaviors, have been proven to be one of the efficient ways to address the internal threats. crom veracity, sensitivity, scalability and robustness in grid trust models and grid reputation systems, this dissertation proposes several new trust models and their corresponding grid reputation systems, and applies these models into the formation of grid virtual organization and grid access control models.The contributions of this dissertation are as follows:1) To solve the rationality, robustness and scalability problems in the grid reputation systems, while depicting the trust relationship between the two unacquainted entities in different inter-organizations, a new trust model and its corresponding grid reputation system are proposed. This model constructs a virtual trust overlay network on top of the grid infrastructure using trust relationships between entities, and regards the organization-level trust relationship as a crucial reference factor based on the global property of virtual trust overlay network, which achieves rational trust evaluation between two entities. The system also resists fake transaction attacks and slander attacks efficiently.2) A new trust model and its corresponding robust grid reputation system with semiautomatic feedback ratings are proposed, and this model is applied for the formation of grid virtual organization, in which, a fine-grained feedback expression model based on the aggregation of objective n op attributes and subjective opinions of evaluators is proposed to enable a personalized and accurate feedback expression semi-automatically. r sing the punishment factor and the adaptive combination of historic trust values and current feedback, the sensitivity of the reputation evaluation in our reputation systems is increased. Moreover, the concept of recommender reputation is introduced into our solution to filter out dishonest recommendations, thus making the reputation system more robust against collusive attacks.3) A trustworthiness-based access control model for virtual organizations, called TwBAC model, is presented. It can express contextual access control policies, and offers the abstraction for resource objects like the roles for subjects. Besides, our model can express the trust relationship of VO members accurately by using trustworthiness, which can also be used to control the depth of delegation. This dissertation also presents an administration model to perform the autonomous management.