USB key requirement.

[Dan Serban <dserban@lodgingcompany.com>]

So, I'm currently switching my 9 workstations around the house to
diskless boot.  They mount nfs shares that reside on top of an
encrypted raid server.  This is all fine and good.

What I'd like to do:

On a specific workstation, on boot, i'd like to require that a specific
usb memory stick be inserted in the system.  ie. one that contains a
key which will allow the boot process to continue.

Can this be done?  If so, what should I use to make it less than easy
to decipher?

Maybe a GPG encoded text file that matches against a plain text one?
(that's insecure)...

I don't know.  Do any of you have any suggestions?