Re: [dmarc-ietf] ARC questions

Michael Thomas <mike@mtcc.com> Sun, 22 November 2020 19:31 UTC

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From: Michael Thomas <mike@mtcc.com>
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Subject: Re: [dmarc-ietf] ARC questions
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On 11/22/20 11:18 AM, Douglas E. Foster wrote:
> ARC has a very limited set of items included in the signature.   Body 
> hash is purposefully excluded.  So it is the same signature algorithm 
> but with different parameters and a different purpose.  Therefore it 
> has a different header label .


Now wait, Kurt just said that the body hash is included. Somebody has to 
be wrong here.

Mike


>
>
> Sent from my Verizon, Samsung Galaxy smartphone
>
>
>
> -------- Original message --------
> From: John R Levine <johnl@taugh.com>
> Date: 11/22/20 2:14 PM (GMT-05:00)
> To: Michael Thomas <mike@mtcc.com>om>, "Kurt Andersen (b)" 
> <kboth@drkurt.com>
> Cc: dmarc@ietf.org
> Subject: Re: [dmarc-ietf] ARC questions
>
> > Is there a reason that there is a separate ARC-signature rather than 
> just
> > using the DKIM signature that is normally created for the new 
> message? Since
> > ARC is new, you'd not want the intermediary to stop DKIM signing the 
> message
> > so you end up with essentially two signatures doing essentially the 
> same
> > thing?
>
> The ARC signature has a sequence number so you can track the chain of
> custody. You are right that it is similar to the DKIM signature but the
> extra ovehead doesn't seem excessive.
>
> Regards,
> John Levine, johnl@taugh.com, Taughannock Networks, Trumansburg NY
> Please consider the environment before reading this e-mail. https://jl.ly
>
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