Thanks for the document update. I have issued the IETF Last Call.

Paul

On Sun, Jan 25, 2026 at 3:15 PM Göran Selander <[email protected]>
wrote:

> Hi Paul,
>
> Thanks for the review!
>
> We just submitted -16 addressing your comments, see responses below.
>
> We agree essentially on everything, details in this pull request:
> https://github.com/cose-wg/CBOR-certificates/pull/302
>
> Thanks,
> Göran
>
>
> *From: *Paul Wouters <[email protected]>
> *Date: *Thursday, 8 January 2026 at 21:55
> *To: *[email protected] <
> [email protected]>
> *Cc: *cose <[email protected]>
> *Subject: *AD review draft-ietf-cose-cbor-encoded-cert-15
>
> Hi,
>
> I've done my AD review of draft-ietf-cose-cbor-encoded-cert-15
>
> I have a few comments and questions, but I think the most important item
> is whether we asked the TLS WG what they think about making the C509 TLS
> Certificate Types RECOMMENDED Y to implement. It seems quite a lift to
> require all TLS servers would implement C509 at this point in time? The
> field is documented to mean:
>
> If the "Recommended" column is set to "N", it does not necessarily
> mean that it is flawed; rather, it indicates that the item either
> has not been through the IETF consensus process, has limited
> applicability, or is intended only for specific use cases.
>
>
> Which I would argue matches better with RECOMMENDED N
>
> [GS] Agree
>
> See the rest of my AD review below,
>
> Paul
>
>
> The Abstract is large and the Introduction repeats many things. Can we
> deduplicate this and make the Abstract smaller and more consise?
>
> Please add a sentence: This document updates RFC 6698 in the Abstract.
>
> [GS] The Abstract is updated and now includes this text.
>
>
>         validityNotAfter: ~time / null,
>
> Why can this be null? I thought X.509 certs always have an end date?
> (reading further, this is explained in 3.1.5)
>
> [GS] Right, the parameters are explained in turn in the following
> subsections. No change made.
>
>         the octets 0xfe and 0xfd are used instead of 0x02 and 0x03
>         in the CBOR encoding to represent even and odd y-coordinate,
>         respectively.
>
> I would prefer to rewrite this without using the "respectively" construct
> to help non-native english speakers.
>
> [GS] Done, see PR.
>
> This does not parse:
>
>         using of the reserved CBOR tag
>
> I assume "of" just needs to be removed?
>
> [GS] Correct, fixed here and in other locations using the same phrase.
>
>
>         An implementation MAY only support c509CertificateRequestType = 0.
>
> This is an odd way of saying, I think, that c509CertificateRequestType = 0
> is mandatory to implement.
>
> [GS] This is a remnant from when there were fewer options / values. Rewritten
> as "An implementation MAY only support certain values of
> c509CertificateRequestType."
>
> There seems to be a spelling error in: TBSCertificatdsveRequest
> Should this be: TBSCertificateRequest ?
>
> [GS] Correct, fixed.
>
>         For example, if the EST server includes a subjectAltName with
>         a partially filled extensionValue, such as iPAddress with an
>         empty byte string, this means that the client SHOULD fill in
>         the corresponding GeneralName value
>
> This makes it appeat the EST server can put in "10.0.2" and the client can
> only
> pick that range, or "example.com" and the client can pick only subdomains
> from
> "example.com", but it is unlikely that you meant this? Perhaps rephrasing
> this
> to avoid this interpretation?
>
> [GS] Thanks, we made the example more explicit in the PR.
>
>
> "Brotli [RFC7932]" is not clarified until after "Brotli" has been
> mentioned a few times already.
> Please move the "[RFC7932]" clarification to the first instance of the use
> of "Brotli".
>
> [GS] Done.
>
> This sentence is unreadable, please rewrite:
>
>         Any issue to decode or parse a C509 certificate should be handled
>         by the certificate using system as would the issue of parsing
>         the corresponding X.509 certificate.
>
> Perhaps:
>
>         Any problems with decoding or parsing a C509 certificate should be
> handled
>         exactly as how such errors would be handled for the corresponding
> X.509 certificate.
>
> [GS] Done.
>
> Section 9.5, should the text "Name and Identifiers are informal
> descriptions" maybe be included
> as a note above the table?
>
> [GS] Done.
>
> Why is Postal Code defined, but not Postal Address? Is that because Street
> Address is used?
>
> [GS] This was discussed in
> https://github.com/cose-wg/CBOR-certificates/issues/255
> and it was decided to not specify it in CBOR since we didn’t see much room
> for simplification.
>
> Section 9.10. C509 Extended Key Usages Registry
>
> A good list of EKUs is:
>
> https://docs.digicert.com/zf/trust-lifecycle-manager/define-policies-to-ensure-compliance/certificate-attributes-and-extensions/extended-key-usage.html
>
> I happen to know (as an IPsec/IKE expert) that some implementations (like
> Microsoft) requires
> EKUs for IPsec which are not defined here.
>
> I guess these can be added later.
>
> [GS] Yes, they can easily be added later.
>
>
> Section  9.17. TLS Certificate Types Registry
>
> This sets the new type to RECOMMENDED. Since this is (currently) very much
> an IoT related document, I am not
> sure if it qualifies as something to be set to RECOMMENDED Y, meaning all
> servers/clients MUST/SHOULD implement
> this. Has there been a conversation with the TLS WG or the Designated
> Experts for this Registry?
>
> [GS] As proposed above, we agree to change this to RECOMMENDED N.
>
>
>
>
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