Content-Based Access Control.

摘要

In conventional database, the most popular access control model specifies policies explicitly for each role of every user against each data object manually. Nowadays, in large-scale content-centric data sharing, conventional approaches could be impractical due to exponential explosion of the data growth and the sensitivity of data objects. What's more, conventional database access control policy will not be functional when the semantic content of data is expected to play a role in access decisions. Users are often over-privileged, and ex post facto auditing is enforced to detect misuse of the privileges. Unfortunately, it is usually difficult to reverse the damage, as (large amount of) data has been disclosed already. In this dissertation, we first introduce Content-Based Access Control (CBAC), an innovative access control model for content-centric information sharing. As a complement to conventional access control models, the CBAC model makes access control decisions based on the content similarity between user credentials and data content automatically. In CBAC, each user is allowed by a metarule to access "a subset" of the designated data objects of a content-centric database, while the boundary of the subset is dynamically determined by the textual content of data objects. We then present an enforcement mechanism for CBAC that exploits Oracles Virtual Private Database (VPD) to implement a row-wise access control and to prevent data objects from being abused by unnecessary access admission. To further improve the performance of the proposed approach, we introduce a content-based blocking mechanism to improve the efficiency of CBAC enforcement to further reveal a more relevant part of the data objects comparing with only using the user credentials and data content. We also utilized several tagging mechanisms for more accurate textual content matching for short text snippets (e.g. short VarChar attributes) to extract topics other than pure word occurrences to represent the content of data. In the tagging mechanism, the similarity of content is calculated not purely dependent on the word occurrences but the semantic topics underneath the text content. Experimental results show that CBAC makes accurate access control decisions with a small overhead.