Access control can be used to ensure that database queries pertaining to sensitive information are not answered. This is not enough to prevent users from learning sensitive information though, because users can combine non-sensitive information to discover something sensitive. Inference control prevents users from obtaining sensitive information via such “inference channels”, however, existing inference control techniques are not private - that is, they require the server to learn what queries the user is making in order to deny inference-enabling queries. We propose a new primitive - private inference control (PIC) - which is a means for the server to provide inference control without learning what information is being retrieved. PIC is a generalization of private information retrieval (PIR) and symmetrically-private information retrieval (SPIR). While it is straightforward to implement access control using PIR (simply omit sensitive information from the database), it is nontrivi...
David P. Woodruff, Jessica Staddon