Enforcing integrity while maintaining secrecy

We consider the role of constraints in maintaining both secrecy and integrity in a multilevel secure database. In a multilevel database, certain integrity and classification constraints create a secrecy problem since data additions, deletions or modifications require accessing data at higher levels. In many cases, however, these constraints may be approximated by a series of simpler constraints, called level-valid constraints. Level-valid constraints do not require access to any data that is classified higher than the data to be modified. Moreover, they meet the integrity requirements since any database state that satisfies the level-valid constraints also satisfies the multilevel constraints. Simple tests are developed to ensure the validity of proposed level-valid constraints and these constraints are derived for common cases of multilevel constraints.