linux-kernel - Re: [dm-devel] dm-crypt performance

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Message-ID: <Pine.LNX.4.64.1304091352320.10025@file.rdu.redhat.com>
Date:	Tue, 9 Apr 2013 14:08:59 -0400 (EDT)
From:	Mikulas Patocka <mpatocka@...hat.com>
To:	Milan Broz <gmazyland@...il.com>
cc:	Mike Snitzer <msnitzer@...hat.com>, dm-devel@...hat.com,
	Andi Kleen <andi@...stfloor.org>, dm-crypt@...ut.de,
	linux-kernel@...r.kernel.org,
	Christoph Hellwig <hch@...radead.org>,
	Christian Schmidt <schmidt@...add.de>
Subject: Re: [dm-devel] dm-crypt performance



On Tue, 26 Mar 2013, Milan Broz wrote:

> - Are we sure we are not inroducing some another side channel in disc
> encryption? (Unprivileged user can measure timing here).
> (Perhaps stupid reason but please do not prefer performance to security
> in encryption. Enough we have timing attacks for AES implementations...)

So use serpent - it is implemented without any data-dependent lookup 
tables, so it has no timing attacks.

AES uses data-dependent lookup tables, on CPU with hyperthreding, the 
second thread can observe L1 cache footprint done by the first thread and 
get some information about data being encrypted...

Mikulas
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