Information Flow Analysis for Probabilistic Timed Automata

In multilevel systems it is important to avoid unwanted indirect information flow from higher levels to lower levels, namely the so called covert channels. Initial studies of information flow analysis were performed by abstracting away from time and probability. Recently, work has been done in order to consider also aspects either of time or of probability, but not both. In this paper we propose a general framework, based on Probabilistic Timed Automata, where both probabilistic and timing covert channels can be studied. We define properties that allow one to express information flow in a timed and probabilistic setting. As an application, we study a system with covert channels that we are able to discover by applying our techniques.