Actor-network procedures: Modeling multi-factor authentication, device pairing, social interactions

Understand

As computation spreads from computers to networks of computers, and migrates into cyberspace, it ceases to be globally programmable, but it remains programmable indirectly: network computations cannot be controlled, but they can be steered by local constraints on network nodes.

• The tasks of "programming" global behaviors through local constraints belong to the area of security.
• The "program particles" that assure that a system of local interactions leads towards some desired global goals are called security protocols.
• As computation spreads beyond cyberspace, into physical and social spaces, new security tasks and problems arise.