A General Framework for Nondeterministic, Probabilistic, and Stochastic Noninterference

Abstract

Abstract. We introduce a notion of stochastic noninterference aimed at extending the classical approach to information flow analysis with fine-grain information describing the temporal behavior of systems. In par-ticular, we refer to a process algebraic setting that joins durational activ-ities expressing time passing through exponentially distributed random variables, zero duration activities allowing for prioritized/probabilistic choices, and untimed activities with unspecified duration. In this setting unifying time, priority, probability, and nondeterminism, we highlight the expressive power of stochastic noninterference with respect to the ex-isting definitions of nondeterministic and probabilistic noninterference. From this comparison, we obtain that stochastic noninterference turns out to be very strict and limiting in real-world applications and, there-fore, requires the use of relaxation techniques. Among them we advocate performance evaluation as a means for achieving a reasonable balance between security requirements and quality