| Computer Supported Cooperative Work (CSCW) is an information system with which people can work collaboratively in order to complete the common mission objectives though ways such as sharing of resources, exchange of information and Co-operation by using of computers and networks. Access Control is an important means to ensure the safety of system through appropriate access management system to achieve the protection of information and resources so that prevent the system information from inappropriate and unauthorized access of users. With the development of computer technology and applications, in particular the development of network applications, the study of CSCW System Access Control has become one of the hot spots of research in computer science.In CSCW environment, access control faces more challenges. Not only should it meet the basic needs of system security, but also meet the special needs such as fine-grained authorization, environmental perception authorization, the scalability supporting security strategy and the distributed features etc. In addition, in order to alleviate the administrative burden of cooperative work system, it is necessary to make the central administrative be implemented decentralized, make the authority administrative more flexible and improve the scalability of distributed systems. However, for the executor of delegation being an arbitrary user entity under the distributed environment; commissioned operation is scattered; the number of users is dynamic and users may also be unknown, which brings a potential safety problem to delegated authority. So that it is necessary to adapt effective measures to solve the delegated authority in security issues.Much attention has been paid to the construction and application of access control model in this paper. So that it can provide a safety and convenient platform for distributed designers by studying a new access control mechanism which is fitted to CSCW. The main work is as follows:1,Propose an access control model supporting Attribute CertificateAccording to the technology of access control based on role and task, a new access control model NT-RBAC was constructed, which associated users with tasks, roles and permissions in collaborative design. Commission is managed flexibly by the validity of attribute certificate which is introduced to task and the mechanism of delegation, which avoids the shortcoming of permissions'control in time. Meanwhile, the time system response to users' authorization is shortened, the authorized security is increased and the access control flexibility is improved. Finally, an instance based on this model was provided which showed that the model can well satisfy the requirement of access control in CSCW.2,Propose an trust oriented delegation modelAccording to the defect of traditional delegation model, Trust-RBAM (Trust-Role Based Delegation Model) was constructed. Trust base was used to extend the role-based access model. The mapping relation was established between users and trust-base, not role. Trust-base is based on a series of contexts, such as users'credibility, the history of users and user evaluation. Trust-base is assigned to roles and roles assigned to permissions so that achieve user's permission to the shared resource. Trust-RBDM overcome shortcomings of role-based access control model and trust-based access control model and establish secure delegated authority mechanism among users relying on transmission of credible chain. As a result, the security of delegated authority was enhanced.3,Implement an access control system based on trust oriented delegation modelThe Trust-RBDM was applied to 3D cooperative design based on HOOPS. The programming environment is VC++.NET 2003. The analysis of instances shows that the results are quite satisfying. |
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