web commit by NealWalfield

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@@ -25,3 +25,36 @@ Alan Karp [identifies][1] 11 security questions:
 
  * Denial of service         Can I be assured of access?
  * Physical security         Who can touch it?
+
+Mark Miller [proposes][2] some ways to think about security relationships:
+
+  [2]: http://www.eros-os.org/pipermail/cap-talk/2008-March/010615.html
+
+A way to talk about security relationships
+
+Permissions channels (necessarily overt in a sensible system) are phisical:
+
+  * Alice gives Bob a car or a car key.
+
+Online overt information channels are visual:
+
+  * Bob can see Carol. Bob can see Carol's car.
+  * (Potential, transitive) overt connectivity is line of sight.
+  * Lack of overt connectivity (including revocation) is occlusion.
+  * Alice tells the Caretaker to turn opaque, blocking Bob's view of Carol.
+
+Offline overt channels are visual but indirect:
+
+  * Bob can see that Kilroy was here.
+
+Online non-overt channels (both covert & side) are auditory:
+
+  * Bob can hear Carol (e.g., hear Carol banging on the wall)
+  * Alice tries to silence (or mute) Carol
+  * Alice deafens Bob (or creates a deaf Bob)
+  * In order for Bob to hear Carol's wall banging, Bob and Carol,
+      must be awake at the same time
+
+Offline non-overt channels are olfactory:
+
+  * Bob can smell that Kilroy was here, even if Kilroy is asleep or dead.