Time and Probability-Based Information Flow Analysis

Abstract

Abstract-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. It is already known that systems that are proved to be secure in a possibilistic framework may turn out to be insecure when time or probability are considered. 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 a Non-Interference security property and a Non Deducibility on Composition security property, which allow expressing information flow in a timed and probabilistic setting. We then compare these properties with analogous ones defined in contexts where either time or probability or neither of them are taken into account. This permits a classification of the properties depending on their discerning power. As an application, we study a system with covert channels that we are able to discover by applying our techniques.

Static Analysis for Proactive Security

“…Regarding our discussion of the lack of compositionality in Sect. 2, it is fair to say that non-interference often just deals with the program in isolation whereas more complex considerations (such as non-deducibility on computation [33]) are required to regain some compositionality.…”

Secure Information Release in Timed Automata

“…Their notion of security is expressed as a non-interference property and it depends on a natural number m, representing a minimum delay between high-level actions such that the low-level behaviors are not affected by the high-level ones. The authors of [17] define a notion of timed non-interference based on bisimulations for probabilistic timed automata which again have high-level (secret) and low-level (public) actions. A somewhat different approach is taken in [12] that studies the synthesis of controllers.…”

C2Hunter: Detection and Mitigation of Covert Channels in Data Centers

“…The changes of these resource properties are in certain regular patterns. An error-corrected four states automata is designed to model the patterns [51,52].…”