Defending a Perimeter

<<Leakage<< Up to Leakage >>Confinement>>

Alice gives Bob a power that she wishes Mallet not to have.  Bob and Mallet are not supposed to be in communication, and Bob does not wish to give the power to Mallet.  Can Mallet break in and take the power anyway?  Preventing this is the problem of Perimeter Security.
 
Operating Systems MMUs
Open Networks Cryptography
Languages Compilers
Interpreters
Verifiers
Hardware Tag bits
Bounds Checks
etc...



Impenetrable Shields 
Firewalls Applet Sandbox
 
Sifting Garbage 
Tempest Timing Attacks
 
Rubber Hose 
Smart cards & Microwaves