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Re: [openpgp] Session-Key-Reuse and Intended Recipient

"Neal H. Walfield" <neal@walfield.org> Tue, 06 June 2023 13:32 UTC

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Date: Tue, 06 Jun 2023 15:32:38 +0200
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From: "Neal H. Walfield" <neal@walfield.org>
To: Kai Engert <kaie@kuix.de>
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Subject: Re: [openpgp] Session-Key-Reuse and Intended Recipient
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Hi Kai,

On Tue, 06 Jun 2023 15:24:32 +0200,
Kai Engert wrote:
> At the recent OpenPGP for email summit [1], we had a session in which
> we discussed the practicality of the Intended Recipient Subpackage
> (IRS) for PGP/MIME email. It was mentioned that it's recommended to
> use protected headers in such messages. With that, the intended
> recipients are already known. Having equivalent information twice,
> e.g. both protected headers with the TO/CC fields, plus IRS, might be
> unnecessarily complex, and MUA implementations might prefer to avoid
> the IRS.

I'm a bit confused.  You talk about the "Intended Recipient"
subpacket, but I think you mean the the "Intended Recipient
Fingerprint" subpacket:

  https://www.ietf.org/archive/id/draft-ietf-openpgp-crypto-refresh-09.html#section-5.2.3.36

That subpacket takes a fingerprint.  to and cc headers contain RFC
2822 mail name-addrs, I think.

If I'm not misunderstanding, then by definition these two fields
contain different information.  Or are you suggesting that a MUA can
consider an email address equivalent to a fingerprint?  If so, how do
you envision that working?

Thanks,

Neal

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