Scheduler-Independent declassification

The controlled declassification of secrets has received much attention in research on information-flow security, though mostly for sequential programming languages. In this article, we aim at guaranteeing the security of concurrent programs. We propose the novel security property WHAT&WHERE that allows one to limit what information may be declassified where in a program. We show that our property provides adequate security guarantees independent of the scheduling algorithm (which is non-trivial due to the refinement paradox) and present a security type system that reliably enforces the property. In a second scheduler-independence result, we show that an earlier proposed security condition is adequate for the same range of schedulers. These are the first scheduler-independence results in the presence of declassification.