Token authentication with web applications

[Ivan Krstic <krstic () fas harvard edu>]

All,

I'm looking for people's experiences with cheap, uncomplicated token 
devices or other physical means of authentication that play nicely with 
more traditional authentication methods in web applications.

The cheapest solutions that came to mind are printing credit-card sized 
s/key cards, or burning mini-CDs with a key and an auth agent for users. 
Obviously, both methods are flawed (s/key cards can be copied down if 
left exposed, and that's assuming they're not taped to the monitor, 
while a stolen CD can be copied and replaced without evidence of 
tampering[1]), but would still raise the security bar at essentially no 
cost. More extensive authentication solutions are usually rather expensive.

Thoughts?

Cheers,
Ivan.


[1] The s/key printed cards at least address this insofar as the user, 
presuming he can be bothered with remembering which of the 100 s/keys he 
used last, can notice that an intruder gained access to the system.