Security Policies

•Policy partitions system states into:

–Authorized (secure)

•These are states the system can enter

–Unauthorized (nonsecure)

•If the system enters any of these states, it’s a security violation

•Secure system

–Starts in authorized state

–Never enters unauthorized state

Confidentiality

•X set of entities, I information

•I has confidentiality property with respect to X if no x Î X can obtain information from I

•I can be disclosed to others

•Example:

–X set of students

–I final exam answer key

–I is confidential with respect to X if students cannot obtain final exam answer key

Integrity

•X set of entities, I information

•I has integrity property with respect to X if all x Î X trust information in I

•Types of integrity:

–trust I, its conveyance and protection (data integrity)

–I information about origin of something or an identity (origin integrity, authentication)

–I resource: means resource functions as it should (assurance)

Availability

•X set of entities, I resource

•I has availability property with respect to X if all x Î X can access I

•Types of availability:

–traditional: x gets access or not

–quality of service: promised a level of access (for example, a specific level of bandwidth) and not meet it, even though some access is achieved