Maintaining Secrecy and Integrity in Multilevel Databases: A Practical Approach

摘要

In a multilevel database, certain integrity constraints create a secrecy problem since they cannot be evaluated without access to data at higher classifications than the classification of the data to be modified. We present a practical approach for enforcing such constraints without sacrificing the secrecy requirements. Our approach requires that the such constraints be rewritten as a collection of level-valid constraints. Level-valid constraints meet the secrecy requirement since their evaluation does not require access to any data that is classified higher than the classification of data to be modified. Moreover, they meet the integrity requirements since any database state that satisfies the level-valid constraints satisfies the original constraints as well. The cost associated with this approach is that trusted processes must be relied upon to make occasional modifications.