Theft of Information in the Take-Grant Protection Model



Bibliographic Information


Questions of information flow are in many ways more important than questions of access control, because the goal of many security policies is to thwart the unauthorized release of information, not merely the illicit obtaining of access rights to that information. The Take-Grant Protection Model is an excellent theoretical tool for examining such issues because conditions necessary and sufficient for information to flow between two objects, and for rights to objects to be obtained or stolen, are known. In this paper we extend these results by examining the question of information flow from an object the owner of which is unwilling to release that information. Necessary and sufficient conditions for such “theft of information” to occur are derived. To emphasize the usefulness of these results, the security policies of complete isolation, transfer of rights with the cooperation of an owner, and transfer of information (but not rights) with the cooperation of the owner are presented; the last is used to model a subject guarding a resource.


This is the manuscript version. The definitive version was published in Journal of Computer Security, 1994/1995, and is available at