[Seat] Re: Fwd: New Version Notification for draft-fossati-seat-expat-02.txt

[Nathanael Ritz <[e-mail]>]

Apologies to the WG, my original reply to Usama didn't include the
[e-mail] mailing list. Our correspondence is below.

**FWD: On Tue, Mar 10, 2026 at 17:37 UTC Muhammad Usama Sardar <
[e-mail]> wrote:**

On 11.03.26 00:25, Nathanael Ritz wrote:

> And I would greatly doubt if the WG maintains any question about your own
capability to produce sound evidence for the security properties outlined
in your draft.

Independent analysis is always good, but it's fine if you think you won't
have time to.

> I do plan to discuss the ProVerif analysis of the models as part of the
presentation, and I look forward to your input. If you have specific
technical questions regarding the model constraints or syntax that you'd
like me to cover, please feel free to share them on the list, or open an
issue on the GitHub repo beforehand so I can ensure they are thoroughly
addressed for the WG.

I'll try but I have some tasks assigned by TLS chairs, and at least 6
presentations to make next week.

-Usama

**On 11.03.26 00:25, Nathanael Ritz wrote:**

Hello Usama,

I appreciate the personal invite to formally model your draft. My analysis
of draft-fossati-seat-early-attestation-03 was driven by two primary
factors: The first was simple curiosity, given the shared design space my
draft has with their -03 revision in particular. I wanted to know how the
original binding I designed for FACTS compared to the binding proposed for
Early Attestation. Second, I noted the formalization gap documented in
their draft, and I anticipated that the need would have gone unmet for some
time had I not volunteered.

In contrast, the security properties of draft-fossati-seat-expat appear
well-established. And I would greatly doubt if the WG maintains any
question about your own capability to produce sound evidence for the
security properties outlined in your draft. At best, I believe it would be
a duplication of effort for me to produce something independently from your
own work-in-progress at this time.

I do plan to discuss the ProVerif analysis of the models as part of the
presentation, and I look forward to your input. If you have specific
technical questions regarding the model constraints or syntax that you'd
like me to cover, please feel free to share them on the list, or open an
issue on the GitHub repo beforehand so I can ensure they are thoroughly
addressed for the WG.

> My position is that [EXPAT] is a simpler, cleaner, and more secure
solution.

Your position is well noted. From my own perspective as an implementer and
systems integrator, I see valid applications for both approaches. After
all, FACTS is effectively a hybrid. I intend to share separate feedback for
both EXPAT and the Use Cases document before the meeting next week to
expand exactly where I see the two approaches fit or may misfit depending
on application context.

On that note, I have a personal hobby project/research prototype of mine
built to explore continuous re-attestation that is heavily influenced by
the EXPAT draft. While that project is not ready to share to the public
yet, I'm mentioning it to clarify that my own position is grounded by
practical hands-on experience.

Cheers,

Nathanael


On Tue, 10 Mar 2026 at 07:22, Muhammad Usama Sardar <
[e-mail]> wrote:

> Hi Nathanael,
>
> I have been doing the formal analysis of our expat draft (see below),
> which I will summarize in the SEAT meeting. My position is that it is a
> simpler, cleaner, and more secure solution.
>
> More formal analysis is obviously always welcome. So I -- as author --
> would very much appreciate if you could do an independent formal analysis
> of our draft and share your perspective.
>
> I think your formal analysis is valuable input, and very much in line with
> the SEAT charter:
>
> The working group will engage with the research community on the
> evaluation and formal analysis of the protocol artifacts in parallel
> with the specification work.
>
> Independent of that, I think we should settle with nothing less than the
> high standards of TLS WG.
>
> I do have a few questions on your models you shared in other threads but I
> also have quite a few presentations for different WGs/RG to make for the
> meeting next week. So I am hoping you will present your formal analysis
> with your draft in the meeting and we'll have some insightful discussions
> over it in the meeting to better understand any differences of
> models/perspectives.
>
> Looking forward to your formal analysis of our draft.
>
> Thanks and best regards,
>
> -Usama
>
>
> On 27.02.26 08:58, Muhammad Usama Sardar wrote:
>
> Hi,
>
> This version adds/updates the following:
>
>    - Security considerations: Race conditions
>    - Security considerations: Timing of remote attestation
>    - Updated Client as Attester
>    - Added Server as Attester
>    - Added operational overview
>
> We welcome any quick feedback and will try to address that until the
> cutoff.
>
> Thanks,
> -Usama
>
>
> -------- Forwarded Message --------
> Subject: New Version Notification for draft-fossati-seat-expat-02.txt
> Date: Thu, 26 Feb 2026 23:36:40 -0800
> From: [e-mail]
> To: Tirumaleswar Reddy.K <[e-mail]>
> <[e-mail]>, Hannes Tschofenig
> <[e-mail]> <[e-mail]>, Ionut Mihalcea
> <[e-mail]> <[e-mail]>, Muhammad Sardar
> <[e-mail]>
> <[e-mail]>, Muhammad Usama Sardar
> <[e-mail]>
> <[e-mail]>, Thomas Fossati
> <[e-mail]> <[e-mail]>, Tirumaleswar
> Reddy <[e-mail]> <[e-mail]>,
> Yaron Sheffer <[e-mail]> <[e-mail]>
>
> A new version of Internet-Draft draft-fossati-seat-expat-02.txt has been
> successfully submitted by Muhammad Usama Sardar and posted to the
> IETF repository.
>
> Name: draft-fossati-seat-expat
> Revision: 02
> Title: Remote Attestation with Exported Authenticators
> Date: 2026-02-27
> Group: Individual Submission
> Pages: 23
> URL: https://www.ietf.org/archive/id/draft-fossati-seat-expat-02.txt
> Status: https://datatracker.ietf.org/doc/draft-fossati-seat-expat/
> HTML: https://www.ietf.org/archive/id/draft-fossati-seat-expat-02.html
> HTMLized: https://datatracker.ietf.org/doc/html/draft-fossati-seat-expat
> Diff:
> https://author-tools.ietf.org/iddiff?url2=draft-fossati-seat-expat-02
>
> Abstract:
>
> This specification defines a method for two parties in a
> communication interaction to exchange Evidence and Attestation
> Results using exported authenticators, as defined in [RFC9261].
> Additionally, it introduces the cmw_attestation extension, which
> allows attestation credentials to be included directly in the
> Certificate message sent during the Exported Authenticator-based
> post-handshake authentication. The approach supports both the
> passport and background check models from the RATS architecture while
> ensuring that attestation remains bound to the underlying
> communication channel.
>
>
>
> The IETF Secretariat
>
>
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