AD Review of draft-ietf-httpbis-unprompted-auth-09

# AD Review of draft-ietf-httpbis-unprompted-auth-09

cc @fpalombini

Thank you for this document, I found it very clear and easy to read. I only have one minor comment and some nits, you can take care of these at the same time as any other comments from IETF last call, which I will initiate now.

Francesca

## Comments

### key exporter

Section 3:
> When a client wishes to uses the Concealed HTTP authentication scheme with a request, it SHALL compute the authentication proof using a TLS keying material exporter [KEY-EXPORT] with the following parameters:

It is not clear to me if this doc uses the original RFC 5705 version (as referenced) or the updated construction by TLS 1.3 (Section 7.5 of RFC 8446). By the way it is referenced, and the way I interpret the "Update" header tag for RFCs, I'd assume 5705 - if my assumption is wrong, maybe some text (and an additional reference to TLS 1.3 in the sentence above) would help remove all ambiguity. Otherwise, has the working group considered using the TLS 1.3 exporter, rather than the RFC 5705 one?

## Nits

### nit

Section 3.2:
>The key exporter context contains the following fields:

A copy paste gone wrong, I assume :) s/context/output?

### Id nits complaints

ID-Nits gives me the following warning:

  == Unused Reference: 'RFC8792' is defined on line 664, but no explicit
     reference was found in the text

This is a false positive, but I think moving the first line of Figure 5 and 6 out of the figure would fix it.

## Notes

This review is in the ["IETF Comments" Markdown format][ICMF], You can use the
[`ietf-comments` tool][ICT] to automatically convert this review into
individual GitHub issues.

[ICMF]: https://github.com/mnot/ietf-comments/blob/main/format.md
[ICT]: https://github.com/mnot/ietf-comments