[CentOS] Securely backing up Linux machines to NAS?

>So what are the simplest options to back up the Linux hosts?   rsync
>does come to mind, but how to do so securely from each host?   I'd
>consider something via ssh, but that would mean an interactive login,
>and encrypting individual files on the hosts is not an option.

Rsync's default transport _is_ ssh, and I understood you can't even change
that in current versions. That's pretty secure and can be automated...