Trusted Computing and Multilevel security Flashcards
Computer Security Models - Bell-LaPadula
formal model for access control
each object has a security class
classes have a strict hierarchy as security levels
top secret > secret > confidential > restricted > unclassified
Subject <- appropriate level and compartment to access an object
has a security clearance
Object <- security classification of a given level
access modes read append write execute
Multilevel security <- multiple categories of levels of data defined
BLP - System of confidentiality
No read up: subject can only read object <= security level
ss-property (simple-security property)
No write down: subject can only write into a object >= security level
*-property
Mandatory Access Control
if DAC
ds-property: an individual/role grant other access to doc based on owner’s direction constrainted by MAC rules.
BLP - Limitations
incompatibility of confidentiality and integrity within a single MLS system
cooperating conspirator in the presence of covert channels
breaks down when untrusted low classified executable data are allowed to be executed by a high clearance trusted subject
Trusted Systems
Trusted system <- system believed to enforce a given set of attributes to a stated degree of assurance
trustworthy system <- system that can provide mathematical proof that an attacker no matter how clever won’t be able to.
