Unauthorized inferences in semistructured databases q

In this paper we study the problem of providing controlled access to confidential data stored in semistructured databases. More specifically, we focus on privacy violations via data inferences that occur when domain knowledge is combined with nonprivate data. We propose a formal model, called Privacy Information Flow Model, to represent the information flow and the privacy requirements. These privacy requirements are enforced by the Privacy Mediator. Privacy Mediator guarantees that users are not be able to logically entail information that violates the privacy requirements. We present an inference algorithm that is sound and complete. The inference algorithm is developed for a tree-like, semistructured data model, selection–projection queries, and domain knowledge, represented as Horn-clause constraints. 2006 Elsevier Inc. All rights reserved. 0020-0255/$ see front matter 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.ins.2006.01.004 q This work was partially supported by the National Science Foundation under grants IIS-0237782 (Farkas), 9734242 (Brodsky), and CCR-0113515 and IIS-0242237 (Jajodia). * Corresponding author. Tel.: +1 803 576 5762; fax: +1 803 777 3767. E-mail addresses: [email protected] (C. Farkas), [email protected] (A. Brodsky), jajodia@ gmu.edu (S. Jajodia). 3270 C. Farkas et al. / Information Sciences 176 (2006) 3269–3299