Dynamic Disclosure Monitor (D2Mon): An Improved Query Processing Solution

The Dynamic Disclosure Monitor (DMon) is a security mechanism that executes during query processing time to prevent sensitive data from being inferred. A limitation of DMon is that it unnecessarily examines the entire history database in computing inferences. In this paper, we present a process that can be used to reduce the number of tuples that must be examined in computing inferences during query processing time. In particular, we show how a priori knowledge of a database dependency can be used to reduce the search space of a relation when applying database dependencies. Using the database dependencies, we develop a process that forms an index table into the database that identifies those tuples that can be used in satisfying database dependencies. We show how this process can be used to extend DMon to reduce the number of tuples that must be examined in the history database when computing inferences. We further show that inferences that are computed by DMon using our extension are sound and complete.