how to change authAuthority in bulk

I'm migrating over users with crypt passwords and need to generate the authAuthority for kerberos and appleFileServer but for the life of me I can't figure out how. I can use the work group manager but I really want to automate it so I can bind against the legacy ldap db to confirm their password before adding it to the new database as they log in to a web interface. Any ideas? Thanks all, Rob J. Caskey UGA School of Music