> It is not: the REST-level (here CoAP) Content-Type is the media-type of the 
> whole thing
Thanks, I overlooked this aspect. That implies that the parameter should, 
instead of 'TBD3' what I thought, describe 'voucher in cbor' for which there is 
no CoAP cf defined. I assume that the number would then fallback to CBOR cf=60, 
which is true (it is 'plain CBOR' even though a specific thing - voucher 
request - is encoded in that CBOR).
I don't see much benefit in including a COSE parameter 'content type = 60' into 
the COSE container to be frank.  A Registrar will anyhow try to decode the 
payload as CBOR and if that fails, it returns 4.00.

From RFC 8152  and draft-8152-bis I don't see that 'content type' is a 
mandatory header parameter. The SHOULD requirement for it doesn't apply to our 
case. (And probably this SHOULD requirement is too vague, if it ought to apply 
to our case.)
Maybe draft-8152-bis text could be updated if me and Michael understand it 
wrongly?  Toerless was also in favor of including the parameter in our case.

> No, no, no…  You just created busywork for interoperability testing.
The idea was not to test additional payload formats (like 18); I just do this 
to let the server be liberal in what it accepts. Technically a cf=18 is not 
wrong here. But agree we don't want to specify any additional format options.
You're right that for current interop testing, to find the bugs, it is better 
to *not* be too liberal.   Further reasons were that TBD3 was not yet defined 
during the testing past years; and that I have some legacy Pledges that use 
cf=18 still.

Esko

-----Original Message-----
From: Carsten Bormann <c...@tzi.org> 
Sent: Thursday, July 22, 2021 02:48
To: Esko Dijk <esko.d...@iotconsultancy.nl>
Cc: Toerless Eckert <t...@cs.fau.de>; 
draft-ietf-anima-constrained-vouc...@ietf.org; anima@ietf.org
Subject: Re: [Anima] draft-ietf-anima-constrained-voucher COSE confusion

> 
>> Now, there is in the COSE header also a parameter paramaeter called "content 
>> type"
> 
> In my implementation I don't use the 'content type' header in COSE because it 
> is duplicate.

It is not: the REST-level (here CoAP) Content-Type is the media-type of the 
whole thing (as packaged in COSE-Sign1), while the COSE content-type is just 
the media-type of the payload.
Except in somewhat unlikely cases, these are not the same.

> For example my servers should also accept content-format 18 just as TBD3.

No, no, no…  You just created busywork for interoperability testing.
Please decide for one option here and stick with that!

Grüße, Carsten

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