Information Flow Analysis in Logical Form

We specify an information flow analysis for a simple imperative language, using a Hoare-like logic. The logic facilitates static checking of a larger class of programs than can be checked by extant type-based approaches in which a program is deemed insecure when it contains an insecure subprogram. The logic is based on an abstract interpretation of program traces that makes independence between program variables explicit. Unlike other, more precise, approaches based on a Hoare-like logic, our approach does not require a theorem prover to generate invariants. We demonstrate the modularity of our approach by showing that a frame rule holds in our logic. Moreover, given an insecure but terminating program, we show how strongest postconditions can be employed to statically generate failure explanations.