@jws Thanks again, useful. @streakmachine @hazardwarning I'd looked at SSH and found SCP yesterdsy.
I've got keys at my Web host, can generate locally if need be, but getting the bloody things to talk to each other is something I'll need to sit down and plan.
Certificates: something that's always previously been managed by software I've been using. Creating my own stuff, simple as it is, brings a new appreciation for designers, developers…
SSH is definitely the way to go. SCP (piggy-backs on ssh) makes remote file copies dead easy.