In a statistical database, it is often desired to allow query access only to aggregate data, not individual records.
Securing such a database is a difficult problem, since intelligent users can use a combination of aggregate queries to derive information about a single individual.
Some common approaches are: For many years, research in this area was stalled, and it was thought in 1980 that, to quote: But in 2006, Cynthia Dwork defined the field of differential privacy, using work that started appearing in 2003.
While showing that some semantic security goals, related to work of Tore Dalenius, were impossible, it identified new techniques for limiting the increased privacy risk resulting from inclusion of private data in a statistical database.
This makes it possible in many cases to provide very accurate statistics from the database while still ensuring high levels of privacy.