Re: [dmarc-ietf] ARC questions

John R Levine <johnl@taugh.com> Wed, 02 December 2020 20:31 UTC

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Date: 2 Dec 2020 15:31:19 -0500
Message-ID: <aafa5e78-aff9-8076-b76f-62f5b3a13fc1@taugh.com>
From: "John R Levine" <johnl@taugh.com>
To: "Michael Thomas" <mike@mtcc.com>, "Brandon Long" <blong@google.com>
Cc: "IETF DMARC WG" <dmarc@ietf.org>
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Subject: Re: [dmarc-ietf] ARC questions
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On Wed, 2 Dec 2020, Michael Thomas wrote:
>> Ignoring the existing usage of DKIM, DKIM+A-R would only work for a single 
>> hop, and lead to some complication compared to the other DKIM signatures 
>> already on the message.
>
> Wait, what? a DKIM signatures survives until it encounters an intermediary 
> that alters the message in a breaking manner. Arc-Signatures are no different 
> in that respect. In fact as far as I can tell they are identical modulo the 
> i= difference.

Please reread the ARC spec.  The ARC-Authentication-Results at level N 
tells you whether the ARC and DKIM signatures were good at level N-1.

R's,
John