Unwinding in Information Flow Security

We study information flow security properties which are persistent, in the sense that if a system is secure then all of its reachable states are secure too. We present a uniform characterization of these properties in terms of a general unwinding schema. This unwinding characterization allows us to prove several compositionality properties of the considered security classes. Moreover, we exploit the unwinding condition to dictate the form of the rules we can use to incrementally develop secure processes and to rectify insecure processes.