Outline for May 12, 1997 1. Greetings and Felicitations a. Please remember to give me write-ups of your vulnerabilities, both what worked and what didn¼t, in the format discussed earlier 2. Take-Grant a. Show bridges (as a combination of terminal and initial spans) b. Show islands (maximal subject-only tg-connected subgraphs) c. canÄshare(r, x, y, G0) iff there is an edge from x to y labelled r in G0, or all of the following hold: (1) there is a vertex y¼¼ with an edge from y¼ to y labelled r; (2) there is a subject y¼ which terminally spans to y¼¼, or y¼ = y¼¼; (3) there is a subject x¼ which initially spans to x, or x¼ = x; and (4) there is a sequence of islands I1, ..., In connected by bridges for which x¼ is in I1 and y¼ is in In . d. Describe canÄsteal; don¼t state theorem 3. Lattice models a. poset, æ the relation b. highest and lowest c. Set of classes SC is a partially ordered set under relation æ with GLB (greatest lower bound), LUB (least upper bound) operators d. Note: is reflexive, transitive, antisymmetric e. Examples: (A, C) æ (A', C') iff A æ A' and C is a subset of C'; LUB((A, C), (A', C')) = (max(A, A'), union(C, C')) GLB((A, C), (A', C')) = (min(A, A'), intersection(C, C')) 4. Bell-LaPadula (informal) a. Go through security levels, categories, compartments b. Describe simple security property (no reads up) and *-property (no writes down) c. State Basic Security Theorem: if it¼s secure and transformations follow these rules, it¼s still secure