Subject: Re: [Rats] Attestation information model in CDDL

From: Henk Birkholz <[email-masked]>
Date: Mon, 27 May 2019 18:25:28 +0200

Hi Laurence,
hi list,

after some lively discussion and some feedback from individuals that use 
CDDL for some time now, the authors of CDDL came to the conclusion that 
it is viable to use CDDL as an information model language - within the 
limits that exist simply due to its design requirements:

For example, there is no notation to express multi-maps. I-D that tried 
to add these concepts stopped doing so at some point. That said, it is 
possible to build an equivalent construct or create corresponding 
notation, if it is actually really required (and it is probably unlikely 
that that is the case here).

Wrt the current JWT/CWT discussion: there are a few things that are 
surprisingly difficult to express in JSON, I think. But luckily, an 
information model does not have to resolve, for example, a "Base64 or 
Base64URL" question (or corresponding padding, for that matter...), as 
an IM is serialization agnostic.

Viele Grüße,

Henk

On 4/18/19 5:08 PM, Laurence Lundblade wrote:
> Hi folks,
> 
> This is to check in as to whether it makes sense to describe the information model for attestation claims (or whatever we end up calling them) in CDDL. This seems like a good idea since it can describe both CBOR and JSON and it is new, shiny and modern.
> 
> There’s a few gaps that will need to be bridged:
> 
> - We definitely want binary strings for lots of the claims (many are hashes) in CBOR, but JSON can’t directly carry binary. Presumably we decide that they will be Base64 or Base64URL encoded in JSON.
> 
> - I can see wanting to use NaN and Infinity for some floating point numbers. They could be very convenient. CBOR can carry them, JSON can’t, so maybe this is handled on a claim-by-claim basis.
> 
> Any other gaps?
> 
> Does this make sense?
> 
> Thanks!
> 
> LL
> 
> 
> 
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