Re: [Cbor] CDDL for COSE + EAT/CWT + SUIT + CoSIWD

Carsten Bormann <> Wed, 08 December 2021 13:26 UTC

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From: Carsten Bormann <>
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Date: Wed, 08 Dec 2021 14:26:42 +0100
Cc: Laurence Lundblade <>, cose <>, "" <>, Henk Birkholz <>
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To: Hannes Tschofenig <>
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Subject: Re: [Cbor] CDDL for COSE + EAT/CWT + SUIT + CoSIWD
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Hi Hannes,

> On 2021-12-08, at 13:46, Hannes Tschofenig <> wrote:
> Hi Carsten,
> I suspect Laurence is sending this email because of his work on EAT. I am arguing that an attempt to improve the CDDL for the mentioned specs will not lead to any improvement at all because the problem is elsewhere. I am saying that because I have just spent many hours reading the EAT spec.

Thank you for clarifying this, providing the RATS perspective that I’m missing here.

I’m glad to hear that EAT only has one problem :-) (“the problem”).

I still think that doing the work I was outlining would help us in various specifications.
And when it comes to EAT, I’m assuming that at some point we want to describe EAT claims with some statements about their structure, which would naturally use CDDL.  But that may not be needed for the initial EAT specification; I haven’t checked that.  If it is not needed, it might be too much of a distraction to apply the work I was outlining to EAT now.

Grüße, Carsten

> Ciao
> Hannes
> -----Original Message-----
> From: Carsten Bormann <>
> Sent: Wednesday, December 8, 2021 1:37 PM
> To: Hannes Tschofenig <>
> Cc: Laurence Lundblade <>; cose <>;; Henk Birkholz <>
> Subject: Re: [Cbor] CDDL for COSE + EAT/CWT + SUIT + CoSIWD
> On 2021-12-08, at 13:30, Hannes Tschofenig <> wrote:
>> EAT by itself is not really an interoperable spec. COSE on its own is not interoperable either.
> If I guess about the definition of "interoperable spec” you are using here, ASCII is not an interoperable spec either - you still have to agree on what the text means…  Still, ASCII was kind of useful as the basis for a lot of interoperability, I think.
> I think the point here was to shape some CDDL that makes it easier to talk about the way a more specific (interoperable?) spec uses COSE (which does have CDDL, just not in a way that usually can be integrated as-is to express the additional constraints a COSE-using specification typically makes).
> Grüße, Carsten
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