Non-interference with What-Declassification in Component-Based Systems

In this paper, we present a novel notion of compositional non-interference for component-based systems. Our specification mechanism for non-interference properties is based on equivalence relations, catering for a precise formalization of declassified information. It takes assumptions on the environment into consideration. We also present a new notion of non-interference for services provided by a component and prove that a component only providing non-interferent services is itself non-interferent. Using these properties, secure information flow in a component-based system can be proved by separately analyzing each of the services that are provided by the components. As a result, we gain modular, precise, and reusable information-flow specifications for component-based systems.