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Re: [COSE] [Cose]: RFC8152(bis) question(s) (draft-ietf-anima-constrained-voucher)

Carsten Bormann <cabo@tzi.org> Thu, 22 July 2021 16:20 UTC

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From: Carsten Bormann <cabo@tzi.org>
In-Reply-To: <20210722160135.GB55573@faui48e.informatik.uni-erlangen.de>
Date: Thu, 22 Jul 2021 18:20:18 +0200
Cc: cose@ietf.org, "draft-ietf-anima-constrained-voucher@ietf.org" <draft-ietf-anima-constrained-voucher@ietf.org>, Esko Dijk <esko.dijk@iotconsultancy.nl>
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To: Toerless Eckert <tte@cs.fau.de>
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Subject: Re: [COSE] [Cose]: RFC8152(bis) question(s) (draft-ietf-anima-constrained-voucher)
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On 22. Jul 2021, at 18:01, Toerless Eckert <tte@cs.fau.de> wrote:
> 
> As far as i could find, none of the examples
> in appendix C nor in https://github.com/cose-wg/Examples do have
> the "content type" (3:) field with a value and none seem to elaborate
> about different type of payloads.

I won’t try to answer the whole question, but let’s just look at one example:
The European Digital Green Card (Covid pass) uses a CWT with claim -260.
Given that the claim -260 is registered in the CWT registry [1], there is no need to provide any other semantics with the signed object.
Similar with the FIDO entries there.

If you do not use a CWT, you may want some other form of identification of what the payload is about, and the COSE content-type header parameter (3) is one of them.

Grüße, Carsten

[1]: https://www.iana.org/assignments/cwt/cwt.xhtml
Scroll down to hcert

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