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From:      "Jeroen C. van Gelderen" <jeroen@vangelderen.org>
To:        Kris Kennaway <kkennawa@physics.adelaide.edu.au>
Cc:        Adam Shostack <adam@breakwater.homeport.org>, nr1@ihug.co.nz, freebsd-security@FreeBSD.ORG
Subject:   Re: secure backup
Message-ID:  <373FEC63.D579485D@vangelderen.org>
References:  <Pine.OSF.4.10.9905171213420.28148-100000@bragg>

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Kris Kennaway wrote:
> 
> On Sun, 16 May 1999, Adam Shostack wrote:
> 
> > You're worried about errors on the tape, I presume?  You could
> > pipe the output of pgp through something that does redundant 
> > encoding, such that errors on the tape are recoverable outside 
> > the tape.  There are some direct tradeoffs that you can find 
> > between bloat and recoverability; as you add bits, your odds 
> > of being able to reconstruct increase.
> 
> Pipe the output of dump or tar or whatever you're using through 
> bdes(1). You don't need the overhead of PGP unless you want a 
> trusted third party to read the backup without knowing the 
> encryption key. 

PGP provides a password based encryption mode, just use that, you will
still benefit from PGPs compression and checksumming facilities.

> Pass the data through three
> rounds of bdes doing an encrypt, decrypt, followed by encrypt (with different
> keys, of course) and you've got yourself 3DES, which bdes doesn't seem to do
> natively. Make the keys random, and stick those in a PGP file if you like.

If you assume PGP is available, why not just use it? Using bdes(1) in
this setup sounds way more complicated (thus error-prone) to me.

> Transport the data stream to the server using ssh -c none (no need for the
> overhead of another encryption layer unless you're really paranoid) 

Just being cautious is enough. Adding a layer of SSH encryption will at
least twarth offline dictionary attacks on the backup passphrase.
Encryption is cheap, why disable it if you don't have to?

Cheers,
Jeroen
-- 
Jeroen C. van Gelderen - jeroen@vangelderen.org - 0xC33EDFDE


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