Outline for January 8, 2007

1. Greetings and Felicitations!
2. Miscellaneous points
   1. Copy flag and right
   2. Own as a special right
   3. Principle of attenuation of privilege
3. What is the safety question?
   1. An unauthorized state is one in which a generic right r could be leaked into an entry in the ACM that did not previously contain r. An initial state is safe for r if it cannot lead to a state in which r could be leaked.
   2. Question: in a given arbitrary protection system, is safety decidable?
   3. Theorem: there is an algorithm that decides whether a given mono-operational system and initial state is safe for a given generic right.
4. General case: It is undecidable whether a given state of a given protection system is safe for a given generic right.
   1. Represent TM as ACM
   2. Reduce halting problem to it
5. Take-Grant
   1. Counterpoint to HRU result
   2. Symmetry of take and grant rights
   3. Islands (maximal subject-only tg-connected subgraphs)
   4. Bridges (as a combination of terminal and initial spans)