I realize some form of this question has been asked many times before but none of the answers I've seen are really what I'm looking for.
I have a server that I'll call S and a backup machine that I'll call B. Right now, S has whole disk encryption and B has no encryption. Since the encryption on S only matters when the machine is powered off, all the files that B gets when it rsyncs into S are unencrypted. Thus, my backups are not encrypted.
Since B is a Netgear ReadyNAS Pro and, according to the people at the ReadyNAS forums, the ReadyNAS can't easily be encrypted, I'm looking for some way to encrypt my data before it gets to the ReadyNAS.
Surely this kind of thing has been done by many people many times before. Rather than only recommending a certain product like Duplicity or ZMANDA, could someone please explain to me the theory behind this? For example, is it ideal to copy the data to the backup disk, then encrypt the disk, or is it better to encrypt the data, then copy it to the backup disk? Please don't just throw a product at me. I'm looking for the "how", not the "what".