[Box Backup] A few questions about BoxBackup

[Gary]

Ben,

> No. This would not do what you want anyway, because the keys to
> decrypt the files are on the local machine. Therefore anyone with 
> sufficient access to the local machine would be able to download 
> the "encrypted" files. For someone on the local machine with access 
> to the keys (ie root or physical access to the box), the files on 
> the store should be considered in plaintext when evaluating security.

That is correct, but I was thinking of backing up some files that I
have on CD-ROMs, etc. to have a backup in case they are lost/damaged
(without the requirement to keep them locally on hard drives). In any
case, perhaps local key storage could be somewhat softened by using key
challenge passwords?

> bbstored cannot recreate the files, because it does not have access
> to the keys.

Right. But it would be possible for the server to re-construct an
encrypted file from rsync slices, md5 it, and send the signature back
to the client. The client could re-entrypt that file locally, generate
another md5, and compare it (without complete re-download).

> What it does is simply send the encrypted checksums that
> the client sent it the last time it was uploaded -- no processing is 
> done on the server. It will send one checksum per block in the file,
> because that is the unit in which is it compressed and encrypted.

Hmmmm, hmmmmm, so, if I understand correctly, for example block-level
hard disk corruption on the server side (in encrypted data area) would
not be detected by -aq, as only (last known) checksums are extracted
from the store by bbstored? Also, should rsync slice implementation
fail (imperfect reconstruction bug), -aq would not detect it either,
right?

> * the load on the client and server
> * the latency of your network link
> * the usage of your network link -- is something uploading or 

As far as I can tell there is nothing going on on client/server, nor on
the network link, but I will keep looking into this.

Gary



		
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