Re: [Rats] What's to EAT? - terminology clarification

[Henk Birkholz <[e-mail]>]

Now I am a bit confused. Didn't you attempt to use CDDL as an 
information model in the EAT I-D?

On 13.11.19 18:49, Laurence Lundblade wrote:
> 
>> On Nov 12, 2019, at 11:12 PM, Schönwälder, Jürgen 
>> <[e-mail] 
>> <mailto:[e-mail]>> wrote:
>>
>> Concerning IMs and DMs, here is the (extended) RFC 3444 view that
>> is commonly used by some parts of the IETF:
>>
>>                 IM               --> conceptual/abstract model
>>                 |                    for designers and operators
>>      +----------+---------+
>>      |          |         |
>>      DM         DM        DM     --> concrete/detailed model
>>      |          |         |          for implementors
>>   +--+--+   +--+--+--+    |
>>   |     |   |  |  |  |    |
>>   EN    EN  EN EN EN EN   EN     --> encodings / representation formats
>>                                      for instance data
> 
> In the EAT draft, the EAT claims information model is in the largely 
> textual description of each claim.
> 
> In the EAT draft there is just one EAT claims data model. It is the CDDL 
> in the EAT draft.
> 
> Currently there are two claims encodings, CBOR and JSON. Thanks to CDDL, 
> we get from data model to encoding in a largely mechanical way and there 
> is little text needed.
> 
> 
>                  IM: Text
>                  |
>                  +
>                  |
>                  DM: CDDL
>                  |
>              +---+--+
>              |      |
>             CBOR   JSON
> 
> 
> I think this is a good, simple and effective way to proceed.
> 
> (There are a few things wrong with the way this is written up in the 
> current EAT draft that need to be fixed:
> - The encodings are mis labeled as the data model
> - I’m not sure the CDDL is correct)
> 
> Maybe one more encoding for X.509/ASN.1/DER is added to cover Dave’s use 
> case. Hopefully it could be by saying how to encode the needed subset of 
> CDDL into ASN.1/DER. Android Keystore also uses X.509 for attestations, 
> so this might add motivation. To keep effort down, CDDL->ASN.1 should 
> just be for EAT and a CDDL subset.
> 
> I do not think we should try to bring YANG in here. So there is no YANG 
> expression of EAT claims. (I did see Eric’s GPS use case, but don’t 
> think it is mainstream enough to motivate the complexity and large 
> effort to bring YANG into play here).
> 
> This email is just about the “EAT claims information model”. There can 
> be other separate information models for other parts of RATS. I don’t 
> think there should be one global RATS information model that spans all 
> the documents.
> 
> The gap of sorts here is IANA registered claims, the existing ones and 
> new ones. There’s no requirement to provide an information model or CDDL 
> when you register new claims with IANA or even coordinate between JWT 
> and CWT.
> 
> LL
> 
> 
> 
> 
> 
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