[cap-talk] Metaphor

Mark Miller erights at gmail.com
Thu Mar 27 13:39:27 EDT 2008

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.

Text by me above is hereby placed in the public domain


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