How can I setup a large ddns service environment with Bind9?

[won seok]

I would like to setup a ddns server that can provide the ddns service
to a few thousands of clients.
I want to know that the bind9 can be a proper solution for this
condition.
If so what operations should I do? 
As I known, the bind9 software require that same authentification key
should be located at client and server simultaneously. If any
administrator want to provide the ddns service to one thousand of
clients, should the server maintain one thousand of authentification
keys ?
I look forward to any help. 
Thanks in advance.