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Re: private key language

David Shaw <dshaw@jabberwocky.com> Wed, 28 December 2005 17:39 UTC

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Date: Wed, 28 Dec 2005 12:11:23 -0500
From: David Shaw <dshaw@jabberwocky.com>
To: ietf-openpgp@imc.org
Subject: Re: private key language
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On Wed, Dec 28, 2005 at 04:17:40PM +0100, Daniel A. Nagy wrote:
> 
> On Wed, Dec 28, 2005 at 09:12:44AM -0500, David Shaw wrote:
> 
> > What weakness in the private key format are you referring to?
> 
> The Klima-Rosa attack: the private material is not bound cryptographically
> to the public material, thus by changing the public material, the attacker
> can reconstruct the private material from just one (corrupted) signature,
> and forge that signature to cover up the attack.
> 
> Please read the Klima-Rosa paper (poor English, but good content), for more
> details.

Sure, I know about the Klima-Rosa attack, but I was under the
impression that the SHA-1 protected secret key format (S2K 254)
prevents the attack.  The text in 5.5.3. Secret Key Packet Formats
certainly says so:

  The reason for this is that there are some attacks on the private
  key that can undetectably modify the secret key. Using a SHA-1
  hash prevents this.

David

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