Unwinding Conditional Noninterference

Noninterference provides a control over information flow in a system for ensuring confidentiality and integrity properties. In the literature this notion has been well studied as transitive noninterference and intransitive noninterference. In this paper we define a framework on the notion of conditional noninterference, which allows to specify information flow policies based on the semantics of action channels. Our new policies subsume the policies of both transitive and intransitive noninterference, and support dynamic requirements such as upgrading and downgrading. We also present unwinding relations that are both sound and complete for the new policies.