A uniform presentation of confidentiality properties

Security (in the sense of confidentiality) properties are properties of shared systems. A suitable model of shared systems, in which one can formally define the term security property and then proceed to catalog several security properties, is presented. The purpose is to present various information-flow properties in a manner that exposes their differences and similarities. Abstraction is the main tool, and everything that is not central to the purpose is discarded. The presentation is generic in the model of computation. The abstraction lays bare a regular structure into which many interesting information-flow properties fall. A shared system is represented by a relation. How this model lets one reason about information flow is discussed and the term information flow property is formally defined. Various information-flow properties are described. Composability and probabilistic security properties are addressed