[CentOS] unison versus rsync

>Another feature of rsync modules that can be useful is that each module can
>specify a user and group thus one can rsync user directories between
>systems where the user names are the same but uid and gid may differ.

I have been looking at this all morning. Is there any way to auth with keys
or something unique so I can script this securely? Iiuc, the only auth is done
through these rsync user/pass pairs unless you do it with hosts etc.

Thanks everyone!
jlc