Outline for January 26, 2007

1. Greetings and Felicitations!
2. Security policies and mechanisms
1. Policy vs. mechanism
2. Secure, precise
3. Observability postulate
4. Theorem: for any program p and policy c, there is a secure, precise mechanism m* such that, for all security mechanisms m associated with p and c, m* m
5. Theorem: There is no effective procedure that determines a maximally precise, secure mechanism for any policy and program
3. Bell-LaPadula Model: intuitive, security classifications only
1. Security clearance, classification
2. Simple security condition (no reads up), *-property (no writes down), discretionary security property
3. Basic Security Theorem: if it is secure and transformations follow these rules, it will remain secure
1. Show categories, refefine clearance and classification
2. Lattice: poset with ≤ relation reflexive, antisymmetric, transitive; greatest lower bound, least upper bound
3. Apply lattice
1. Set of classes SC is a partially ordered set under relation dom with glb (greatest lower bound), lub (least upper bound) operators
2. Note: dom is reflexive, transitive, antisymmetric
3. Example: (A, C) dom (A′, C′) iff AA′ and CC′; lub((A, C), (A′, C′)) = (max(A, A′), CC′), glb((A, C), (A′, C′)) = (min(A, A′), CC′)
4. Simple security condition (no reads up), *-property (no writes down), discretionary security property
5. Basic Security Theorem: if it is secure and transformations follow these rules, it will remain secure
6. Maximum, current security level
5. BLP: formally
1. Elements of system: si subjects, oi objects
2. State space V = B×M×F×H where:
B set of current accesses (i.e., access modes each subject has currently to each object);
M access permission matrix;
F consists of 3 functions: fs is security level associated with each subject, fo security level associated with each object, and fc current security level for each subject;
H hierarchy of system objects, functions h: O→P(O) with two properties:
1. If oi oj, then h(oi) ∩ h(oj) = ∅
2. There is no set { o1, ..., ok } ⊆ O such that for each i, oi+1h(oi) and ok+1 = o1.