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Re: Encrypted remote backups & issues
At 12:43 Uhr -0400 19.09.2003, Michael Richardson wrote:
> And, you'd like them encrypted on the remote system, not just protected
>between local and remove systems?
yes. It's about doing backups from my single most trusted machine,
too, so I must prevent any sensitive information to leave this
machine unencrypted completely.
> Christian> 2. I realize that cryptoloop does not use checksums/signatures
> Christian> at all. Of course that means that an attacker can easily
> Christian> destroy my backup volume while in transit or while stored on
> Christian> the (broken in) backup server in subtle ways, so that I won't
>
> That's where the NFS underlying layer to a large file might be a better
>choice than NBD.
It's not any different regarding secure cryptographic hashes than NBD
- I even think they need *both* a secure transport layer (ssh tunnel
or ipsec) to give any reliability against modification while in
transit. And regardless from this, if I can't trust the server, I
need crypto hashes with the key *I* am using in the encryption part
of the archive -> which means inside crypto-loop. If crypto-loop does
encryption but not encrypted checksums, there's basically no way to
add that in back later. One could create signatures of the whole
*encrypted* data and encrypt that signature ex post (with the same
key being used by crypto-loop), *but* if I don't store the encrypted
data on a trusted host, I can't create a trusted signature there
either. So the signature must be generated before the data leaves the
trusted machine - and since data leaves the machine in blocks that
only crypto-loop and nbd know about, checksumming must be built into
nbd or crypto-loop. Of course the latter would be the preferred way.
Now, independently of the above security considerations, do you mean
that accessing a large file through NFS for crypto-loop purposes is
going to be more stable than accessing it through NBD? Both NFS and
NBD are in the kernel, and while NBD is *meant* to deliver block
devices accessible by other kernel code, NFS files are meant to be
accessed from userspace, so I have some doubt as to whether NFS files
would be less prone to deadlocks when used for crypto-loop.
Christian.
-
Linux-crypto: cryptography in and on the Linux system
Archive: http://mail.nl.linux.org/linux-crypto/