Access Log
Use a hash of the access log as an additional kind of password. The access log (Computer/Access Time/Access ID) is known to the client and the server. Intruders would need to listen and record the communication from the beginning.
 heise online - 29.05.09 - Ide...
http://www.heise.de/newsticker/Identity-Management-OpenID-mit-openid4java--/meldung/139607
Register Computers
Identify Computer
Identify computers as automatically as possible.

Allow to register computers, allowed to access.

/livcos.org/data/map/brainstorm/AccessSecurity