Security in Computing, Third Edition

5.3. Models of Security

In security and elsewhere, models are often used to describe, study, or analyze a particular situation or relationship. In particular, security models are used to

• test a particular policy for completeness and consistency

• document a policy

• help conceptualize and design an implementation

• check whether an implementation meets its requirements

We assume that some access control policy dictates whether a given user can access a particular object. We also assume that this policy is established outside any model.

That is, a policy decision determines whether a specific user should have access to a specific object; the model is only a mechanism that enforces that policy. Thus, we begin studying models by considering simple ways to ...