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Re: NIST publishes new DSA draft

David Shaw <dshaw@jabberwocky.com> Mon, 20 March 2006 21:51 UTC

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Date: Mon, 20 Mar 2006 16:35:23 -0500
From: David Shaw <dshaw@jabberwocky.com>
To: Tony Hansen <tony@att.com>
Cc: OpenPGP <ietf-openpgp@imc.org>
Subject: Re: NIST publishes new DSA draft
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No, it is not the same output, but it is the same amount of security.
Which hash and which IV doesn't matter here - just that the end result
is 224 bits long.

David

On Mon, Mar 20, 2006 at 04:08:28PM -0500, Tony Hansen wrote:
> 
> Just a quibble. Truncating sha-256 down to 224 bits does not give the
> same output as sha-224, as sha-256 and sha-224 use different
> initialization vectors. So "truncated sha-256" and "sha-224" really
> would be totally different hash values.
> 
> No comment on the rest of what you say.
> 
> 	Tony Hansen
> 	tony@att.com
> 
> David Shaw wrote:
> > I understand the argument about wanting 128 bits of security, but
> > since the new DSA allows a 224 bit q, there just isn't room for 128
> > bits of security.  Whether we truncate SHA-256 and call it "truncated
> > SHA-256" or truncate SHA-256 and call it "SHA-224", we have to
> > truncate.

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