Daniel Widyono said

>We have a user creation script which does this at account setup time.  It's a
>pain when someone clobbers their authorized_keys file or their actual keys
>for whatever reason (being human...).  Has anybody every used host based
>authentication for purely cluster-internal SSH authorization, as opposed to
>passwordless keys for each user, and would care to share their experience?
>
>  
>

Well, right now there is not many users for me to do experiment 
(actually I occupied a whole cluster),
but I think that the following webpage contains what you need.
How about you trying it out and telling us whether it works fine? 8)

http://www.ssh.com/support/documentation/online/ssh/adminguide/32/Host-Based_Authentication.html

Best regards,
Kuo Kan LIANG
Division of Mechanics,
Research Center for Applied Sciences,
Academia Sinica, Taiwan