[Techtalk] Using rsync to remote backup encrypted files?
Terri Oda
terri at zone12.com
Tue Oct 7 17:04:12 UTC 2008
I'd be awfully suspicious about using any service that claims to
have gotten around this problem. Basically, the best encryption gives
away as little info as possible, so changing one byte in the original
has to change a bunch of things (possibly everything) in the encrypted
version, making rsync less useful. Working around that likely means
giving away additional information, so you'd be weakening the security
guarantees provided by the encryption. You could get some traction
from a streaming block cipher if you're only changing the end of the
file, maybe, but assuming you're just using gpg, you're probably out
of luck.
If you're working with all servers you control, you can decrypt-rsync-
reencrypt, but that means (at least) two machines would have access to
the secret keys, which may or may not be desirable depending on your
setup.
On 2008-Oct-6, at 3:22 PM, Kelly Jones wrote:
> I use rsync to backup files remotely.
>
> This works great if they're unencrypted: a small change in a large
> file requires very little bandwidth to sync.
>
> But if I encrypt files, this no longer works: a small change in a
> large file could result in a completely different file, so I lose the
> benefit of rsync.
>
> How do people workaround this? I know online backup companies (like
> mozy.com) must solve this problem somehow?
>
> --
> We're just a Bunch Of Regular Guys, a collective group that's trying
> to understand and assimilate technology. We feel that resistance to
> new ideas and technology is unwise and ultimately futile.
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