Can one still run with des/cookie xauthentication when one does that?
   Normally xdm hides away an authentication file, such as
   /var/run/authdir/authfiles/A:0-00221a so that all involved parties can
   have access to the same authentication keys.


see the ":0" bit there?  that's the $DISPLAY.  the authfile for the
machine i'm sitting at is named `Aelisha.eterna.com.au:0-00236b'.