Security models

Security models are specific mechanisms to represent security policies in a logical way. These models are based on the Trusted Computing Base (TCB), which is described in the US Department of Defense Standard 5200.28. This standard is also known as the Orange Book. It presents TCB as trusted system components that are responsible for the access control to any system. TCB is limited by an fictional boundary called a security perimeter. Every connection between the TCB and other subsystem should be possible using secure channels sometimes named security paths. Security models are present to prevent unauthorized information flow. In other words, they assert that the information is flowing from a low-level security to a high level, and not the opposite. There are also other models named noninterference models, which focus on the behaviors done on each subject and not...