Protection in operating systems

TLDR

The safety problem in protection systems is to determine whether a subject can acquire a particular right to an object. The study presents a model of protection mechanisms in computing systems and argues for its appropriateness. The authors develop a formal model of protection mechanisms in computing systems. In restricted cases the safety problem is decidable, but in general it is undecidable under weak assumptions, with implications discussed.

Abstract

A model of protection mechanisms in computing systems is presented and its appropriateness is argued. The “safety” problem for protection systems under this model is to determine in a given situation whether a subject can acquire a particular right to an object. In restricted cases, it can be shown that this problem is decidable, i.e. there is an algorithm to determine whether a system in a particular configuration is safe. In general, and under surprisingly weak assumptions, it cannot be decided if a situation is safe. Various implications of this fact are discussed.