On the decidablity of model-checking information flow properties

Abstract. Current standard security practices do not provide substan-tial assurance about information flow security: the end-to-end behav-ior of a computing system. Noninterference is the basic semantical con-dition used to account for information flow security. In the literature, there are many definitions of noninterference: Non-inference, Separabil-ity and so on. Mantel presented a framework of Basic Security Predicates (BSPs) for characterizing the definitions of noninterference in the litera-ture. Model-checking these BSPs for finite state systems was shown to be decidable in [8]. In this paper, we show that verifying these BSPs for the more expressive system model of pushdown systems is undecidable. We also give an example of a simple security property which is undecidable even for finite-state systems: the property is a weak form of non-inference called WNI, which is not expressible in Mantel’s BSP framework.