Re: [openpgp] New fingerprint: to v5 or not to v5

Peter Gutmann <> Thu, 08 October 2015 15:17 UTC

Return-Path: <>
Received: from localhost ( []) by (Postfix) with ESMTP id 8EB401A6F8E for <>; Thu, 8 Oct 2015 08:17:12 -0700 (PDT)
X-Virus-Scanned: amavisd-new at
X-Spam-Flag: NO
X-Spam-Score: -1.9
X-Spam-Status: No, score=-1.9 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, T_FILL_THIS_FORM_SHORT=0.01, T_RP_MATCHES_RCVD=-0.01] autolearn=ham
Received: from ([]) by localhost ( []) (amavisd-new, port 10024) with ESMTP id fQYTIuXw3szv for <>; Thu, 8 Oct 2015 08:17:11 -0700 (PDT)
Received: from ( []) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (No client certificate requested) by (Postfix) with ESMTPS id BB86F1A8AFE for <>; Thu, 8 Oct 2015 08:16:53 -0700 (PDT)
DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple;;; q=dns/txt; s=mail; t=1444317413; x=1475853413; h=from:to:cc:subject:date:message-id:references: in-reply-to:content-transfer-encoding:mime-version; bh=kMBlks9YgNp5UOgXUVB2oNF6WZszauGD95NrlfNLaXk=; b=hAqtxq9CSkNg8OhYAOO+/K1cJj8+OSZX5meCKkhjHnTzzdnvr/ngGFAU AGRH7dWganqVmFilxCD88RyO6pLCm04GjOTb1mauBHcIAs5yt95BNd/wy eZC7cAs4F19AwM1Nvvb38apG5T1Atowg1v7iOFDLCHduAWOjwDQvF8i1M NH+L2G8C3T2WSFh93eDtKoqCnqYuvhLx7xQhggF8YspM6bxeBNfN/4ZLk TbVsuq5m8LLUtYxZoBT2v40SQLgKVNvtyId9G9+GFo+QmxUbeD6U9RGwC 7WNmTqIR97PZCeNx9maWILwv8r+DmG2sJwR1LdfX0gB+EEC2VtI+y9jMj g==;
X-IronPort-AV: E=Sophos;i="5.17,655,1437393600"; d="scan'208";a="47361759"
X-Ironport-Source: - Outgoing - Outgoing
Received: from (HELO ([]) by with ESMTP/TLS/AES128-SHA; 09 Oct 2015 04:16:52 +1300
Received: from ([]) by ([]) with mapi id 14.03.0174.001; Fri, 9 Oct 2015 04:16:52 +1300
From: Peter Gutmann <>
To: Werner Koch <>
Thread-Topic: [openpgp] New fingerprint: to v5 or not to v5
Thread-Index: AQHRATcNGRFnZAPwNU68Rcs3/4z3Np5hta52
Date: Thu, 8 Oct 2015 15:16:50 +0000
Message-ID: <>
References: <> <> <> <> <> <> <> <> <> <> <>, <>
In-Reply-To: <>
Accept-Language: en-NZ, en-GB, en-US
Content-Language: en-NZ
x-originating-ip: []
Content-Type: text/plain; charset="us-ascii"
Content-Transfer-Encoding: quoted-printable
MIME-Version: 1.0
Archived-At: <>
Cc: Watson Ladd <>, Phillip Hallam-Baker <>, Daniel Kahn Gillmor <>, IETF OpenPGP <>
Subject: Re: [openpgp] New fingerprint: to v5 or not to v5
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: "Ongoing discussion of OpenPGP issues." <>
List-Unsubscribe: <>, <>
List-Archive: <>
List-Post: <>
List-Help: <>
List-Subscribe: <>, <>
X-List-Received-Date: Thu, 08 Oct 2015 15:17:12 -0000

Werner Koch <> writes:

>Which is not defined by any standard.

You don't need a standard to tell you that a SHA-1 hash of a certificate is
obtained by taking a certificate and hashing it with SHA-1.  Pretty much
everything has supported this for years, typically under the name of
certificate fingerprint.

>It will only take a few days until the first wags create multiple different
>keys with the same identifier to confuse software.

X.509 has been using this mechanism for about twenty years without any
problems.  Sure, someone could do that, but what would they gain by it?  The
same wags could create a key with a colliding email address attached to it,
and they've been able to do that for twenty years as well but the world hasn't
ended because of it.

>I call this corrupt data.  The self-signature would not verify and thus the
>key is unusable.  Time to remember where you stored the backup.

It's not corrupted, someone just updated their key info, the signatures on the
new key data are all valid.  The fact that the exact same key that was used
earlier, with the exact same name/email address attached to it, now has a
totally different identifier associated with it, is a problem with how PGP
identifiers are handled.  No data corruption has taken place.