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Date:      Wed, 19 Jan 2011 23:45:13 +0100
From:      Roland Smith <rsmith@xs4all.nl>
To:        freebsd-questions@freebsd.org
Subject:   Re: harddrive encryption
Message-ID:  <20110119224513.GA4263@slackbox.erewhon.net>
In-Reply-To: <20110118171550.GA64143@slackbox.erewhon.net>
References:  <4D34A6EF.30600@alokat.org> <20110117225308.GA40523@slackbox.erewhon.net> <AANLkTinruOxi_1FFDZzfhSojk1u%2B_XfGsJkDiSbMOuMW@mail.gmail.com> <20110118070719.GA51692@slackbox.erewhon.net> <20110118161040.GC76347@libertas.local.camdensoftware.com> <20110118171550.GA64143@slackbox.erewhon.net>

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On Tue, Jan 18, 2011 at 06:15:50PM +0100, Roland Smith wrote:
> > What do you folks think of the relative merits of AES vs Blowfish for
> > disk encryption?
>=20
> Neither have been broken with their complete number of rounds. Versions of
> both can be broken with a reduced number of rounds. See
> http://www.schneier.com/paper-blowfish-oneyear.html for some analysis of
> blowfish, and e.g. http://www.schneier.com/paper-rijndael.html for several
> attacks on Rijndael with reduced rounds.

It seems I have to correct myself here. According to a presentation by Colin
Percival [1] (slides [2]), blowfish is not safe because it uses a relatively
small block size (for compatibility with DES, IIRC), which makes it more
likely that you can get two identical blocks of (cypher)text in one message,
giving an attacker an avenue of attack.

His recommendation is to use AES. This is wat geli(8) recommends as well.

[1]: http://blip.tv/file/3627639
[2]: http://www.bsdcan.org/2010/schedule/attachments/135_crypto1hr.pdf

Roland
--=20
R.F.Smith                                   http://www.xs4all.nl/~rsmith/
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