Probabilistic Information Flow in a Process Algebra

We present a process algebraic approach for extending to the probabilistic setting the classical logical information flow analysis of computer systems. In particular, we employ a calculus for the analysis of probabilistic systems and a notion of probabilistic bisimulation in order to define classical security properties, such as nondeterministic noninterference (NNI) and nondeducibility on compositions (NDC), in the probabilistic setting. We show how to (i) extend the results known for the nondeterministic case, (ii) analyse insecure nondeterministic behaviors, and (ii) reveal probabilistic covert channels which may be not observable in the nondeterministic case. Finally, we show that the expressiveness of the calculus we adopt makes it possible to model concurrent systems in order to derive also performance measures.