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 ...

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