File produced by koha-dump should be encrypted. It contents personal data. It's GDPR related stuff.
I do not think it is Koha's job to deal with that.
We could create a wiki page to explain people how to encrypt their dump if they do not know how to.
I am sure good sysadmins will use their own workflow and will not trust any --encrypt flags we are going to provide them.
If there is an elegant way to do that, I'm not opposed to somebody providing a patch.
I don't see how this would work in an automated process. I guess there would be a passphrase and/or key file on the same server. Not to speak of the actual Koha installation and database running on that server. If somebody has access to the server, they don't need the backup files to access personal data?
Everything that happens afterwards (transferring backups to a different server etc.) is a custom workflow anyway, sysadmins could apply encryption during that process.
It can be option (parameter) in backup cronjob. I thing that really relevant for cases when backups are tranfering on on other servers/storage.