April 16, 2025 Outline

Reading: text,§5.1–5.2.2, A
Assignments: Project selection, due April 16; Homework #2, due April 28

Module 16 (text, §Appendix A)

1. Lattices

Module 17 (text, §5.1–5.2.2)

2. Bell-LaPadula Model: intuitive, security classifications only
   1. Level, categories, define clearance and 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

3. Bell-LaPadula Model: intuitive, now add category sets
   1. 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 A ≤ A′ and C ⊆ C′;
         lub(A, C), (A′, C′)) = (max(A,A′), C ∪ C′); and
         glb((A, C), (A′, C′)) = (min(A, A′), C ∩ C′)
   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

4. Maximum, current security level

5. Example: Trusted Solaris

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ECS 235B, Foundations of Computer and Information Security Version of April 15, 2025 at 7:17PM

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