Date: Thu, 14 Aug 2003 10:53:20 -0600
From: Val Henson <val@nmt.edu>
To: Matt Mackall <mpm@selenic.com>
Cc: "Theodore Ts'o" <tytso@mit.edu>, James Morris <jmorris@intercode.com.au>,
       Jamie Lokier <jamie@shareable.org>,
       linux-kernel <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@osdl.org>, davem@redhat.com
Subject: Re: [RFC][PATCH] Make cryptoapi non-optional?
Message-ID: <20030814165320.GA2839@speare5-1-14>
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On Tue, Aug 12, 2003 at 11:06:14PM -0500, Matt Mackall wrote:
> On Tue, Aug 12, 2003 at 11:20:38PM -0400, Theodore Ts'o wrote:
> 
> > The real issue is discarding information.  By folding, we hide
> > information about the output of the SHA hash that will hopefully deny
> > information that a Very Sophisticated Attacker (say, at the level of a
> > certain agency that designed the SHA algorithm) that might make it
> > easier for them to attack the SHA algorithm.
> 
> I'll buy that. However simply dropping the data would serve this
> purpose better. As would hashing less than the entire pool on each
> read. 

I agree.  Throwing away 80 bits of the 160 bit output is much better
than folding the two halves together.  In all the cases we've
discussed where folding might improve matters, throwing away half the
output would be even better.

-VAL
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