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Domain 3: Security Architecture and Engineering - Security Models

Q: What are the properties of Security Models?

Simple security property: Describes rules for read Star * security property: Describes rules for write Invocation property: Rules around invocations (calls), such as to subjects

Q: What Security Models are about Integrity?

Biba State machine model (SMM) Clark-Wilson Access control triple Goguen-Meseguer THE noninterference model Sutherland preventing interference (information flow and SMM)

Q: What Security Models are about Confidentiality?

Bell-LaPadula -> government (DoD) No read up, no write down Brewer and Nash aka “Chinese Wall” Take Grant Employs a “directed graph”

Q: What is the definition of a State Machine Model?

Describes a system that is always secure no matter what state it is in . Based on the computer science definition of a finite state machine (FSM). A state is a snapshot of a system at a specific moment in time. All state transitions must be evaluated. If each possible state transition results in another secure state, the system can be called a secure state machine.

6 important questions on Domain 3: Security Architecture and Engineering - Security Models

What is the purpose of a Security Model?

Provides a way for designers to map abstract statements into a security policy:

Determine how security will be implemented, what subjects can access the system, and what objects they will have access to.

What are the properties of Security Models?

Simple security property: Describes rules for read
Star * security property: Describes rules for write
Invocation property: Rules around invocations (calls), such as to subjects

What Security Models are about Integrity?

Biba
State machine model (SMM)
Clark-Wilson
Access control triple
Goguen-Meseguer
THE noninterference model
Sutherland
preventing interference (information flow and SMM)

What Security Models are about Confidentiality?

Bell-LaPadula -> government (DoD)
No read up, no write down

Brewer and Nash
aka “Chinese Wall”

Take Grant
Employs a “directed graph”

What is the definition of a State Machine Model?

Describes a system that is always secure no matter what state it is in.
Based on the computer science definition of a finite state machine (FSM).
A state is a snapshot of a system at a specific moment in time. All state transitions must be evaluated.
If each possible state transition results in another secure state, the system can be called a secure state machine.

What is the definition of an Information Flow Model?

Focuses on the flow of information
Information flow models are based on a state machine model
Biba and Bell-LaPadula are both information flow models
Bell-LaPadula preventing information flow from a high security level to a low security level
Biba focuses on flow from low to high security level