Re: Secure backup on remote untrusted server over slow line?

From: Preben Bohn (preben_bohn@yahoo.com)
Date: 06/12/02 

Date: Wed, 12 Jun 2002 18:26:22 +0200
From: Preben Bohn <preben_bohn@yahoo.com>

Iwo Mergler wrote:
> If you do it blockwise, you can't have the filesystem mounted at the same
> time.

I thought so... :-)

> Use a backup program to create a single file. Compress it, split off the
> header and keep it on the local machine. Encrypt the rest with something
> secure and send it.

Huh? But then I need to send 10GB, and that'll take too long time,
considering that maybe only 1MB is changed per day.

> If you want a reasonably simple, but safe encryption, you could generate
> a key from truly unpredictable data (record your local waterfall) which
> is as long as the file you want to send. XOR the data with it, bit by bit.
> Same for decryption. As long as nobody can get hold of the CD-ROM with the
> key, the code is virtually unbreakable.

Yes, this is fast, but I don't agree that it is virtually impossible to
break it. However the big problem is how to transfer an encrypted 10GB
file (e.g tar-file) incremntally... I can always figure out the
encryption algorithm later (I though about IDEA or DES or something, but
maybe this is too slow).

> On the other hand, you could write the backup to a CD-ROM in the first
> place. :^)

Well, this would be ~14 CD's per day, manually, so... :-)

Best regards

Preben

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