| Our research work includes the research in network security file system,and moreover the certain research in index algorithm of information retrieval.The work in network security file system: based on LDAP and SSHprotocols, we design and implement network security file system. The systemprovides not only security operation over file resources, and also flexiblesecurity policy schema to do fine grain access control over users and fileresources. Moreover, we seperate security policy, access control informationand user information from file system into one center policy managementserver, which specially manages all kinds of data and execute securityauthentication and fine grain authorization control for data directory. Throughthese methods, file resources can be access in high security.In order toimprove the stablity and availability, we adopt mature security protocols,algorithm and data management product.The whole system includes three subsystems: client system, secure fileserver and center policy server. Under windows platform, we design andimplement client system, which is embeded the file explorer and provide theentry for accessing server;design and implement secure file system, whichprovide secure network file serve for users;design the data model and securitypolicy for center policy server. In the thesis, after basicly introducing securityfile system, network file system and related technology, our thesis analyseswhole system solution and security schema in detail, and present concretmodels and essential technical point.The work in index algorighm of information retrieval: based n-gramtechnical, we propose a novel fast indexing approach for information retrieval.Compared with traditional n-gram model, our approach obtains moreremarkable efficiency, especially for long sequence retrieval, and obtain O(1)time complexity in retrieving. Our thesis analyzes the theoretical model, theconcret algorithms, the performance comparison and one experiment systemfor information retrieval. |
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