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