Kerberos and su to root

[Chris Telting]

I have multiple systems and jails at my home.  I would very much like to 
implement a single sign on strategy with kerberos.  I think it's safer 
than having private keys on every single box.  I can easily do this for 
shh user logins to multiple boxes.  But I like to sign in as a user and 
then su to root when I get there.  (Forget about sudo, I am 
administering these boxes and don't want to type sudo for every single 
command, it's not a user machine).  From what I understand of Kerberos I 
would need change identity and type a password every time I ksu which is 
what I'm trying to avoid.

Am I right that it is imposable to maintain multiple simultaneous 
credentials and get the right one to automatically be used?