I have setup remote administration using yast and VNC is working just fine
but I'd like it to require a password before the vnc session is made.

I know that this can be done by running vncserver manually and entering a
password but then it doesn't give you the login screen to chose which user
to login as.

I'd like a password prior to the vnc session becuase without an attacker
can see the list of users in the "login" dialog box and can try to figure
out the root password by hitting the "shutdown" button.

When you enable VNC through the Yast Remote Adminstration where is storing
the vnc config?