Architectural refinement and notions of intransitive noninterference

Abstract

Abstract This paper deals with architectural designs that specify components of a system and the permitted flows of information between them. In the process of systems development, one might refine such a design by viewing a component as being composed of subcomponents, and specifying permitted flows of information between these subcomponents and others in the design. The paper studies the soundness of such refinements with respect to a spectrum of different semantics for information flow policies, including Goguen and Meseguer’s purge-based definition, Haigh and Young’s intransitive purge-based definition, and some more recent notions TA-security, TO-security and ITO-security defined by van der Meyden. It is shown that all these definitions support the soundness of architectural refinement, for both a state- and an action-observed model of systems. A notion of systems refinement in which the information content of observations is reduced is also studied. It is also shown that refinement preserves weak access control structure, an implementation mechanism that ensures TA-security.