[OAUTH-WG] Re: Explicit typing of SD-JWTs (was SD-JWT architecture feedback)

[Dick Hardt <[e-mail]>]

I am trying to make a few points. My reference to the BCP was on the
recommendation to do explicit typing. I'm suggesting that the sd-jwt
document state that include "typ" is a requirement, and to be explicit in
what that value should be.

I would suggest that value be "sd-jwt"

The "application+" mechanism was already deployed when we wrote the BCP --
too late to change that. But sd-jwt is a new token format and can learn
from implementation challenges in the past.



On Sat, Sep 21, 2024 at 9:17 PM Michael Jones <[e-mail]>
wrote:

> Actually, the JWT BCP (which we were both authors of) does not recommend
> using a single media type.  Rather, it recommends using a specific media
> type suffix in the “typ” values
> <https://www.rfc-editor.org/rfc/rfc8725.html#name-use-explicit-typing>:
>
> When explicit typing is employed for a JWT, it is *RECOMMENDED* that a
> media type name of the format "application/example+jwt" be used, where
> "example" is replaced by the identifier for the specific kind of JWT.
>
>
>
> SD-JWT is doing the same thing, recommending the use of the media type
> suffix “+sd-jwt”.
>
>
>
> This enables more fine-grained explicit typing.  For instance, when doing
> explicit typing for an SD-JWT in the Example use case, the “typ” value
> would be “example+sd-jwt”.  This can then be distinguished from an SD-JWT
> for the Other use case, which would use the “typ” value “other+sd-jwt” –
> meeting the goal of explicit typing.
>
>
>
>                                                                 -- Mike
>
>
>
> *From:* Dick Hardt <[e-mail]>
> *Sent:* Saturday, September 21, 2024 9:16 AM
> *To:* Daniel Fett <[e-mail]>
> *Cc:* [e-mail]; [e-mail]
> *Subject:* [OAUTH-WG] Re: SD-JWT architecture feedback
>
>
>
> …
>
>
>
> *Explicit Typing*
>
> Why leave the typing in the header to be determined by the application
> (10.11), and not just be 'sd-jwt' and be REQUIRED?
>
> We had extensive discussions around typing, please refer to the following
> issues:
>
> - https://github.com/oauth-wg/oauth-selective-disclosure-jwt/issues/267
>
> - https://github.com/oauth-wg/oauth-selective-disclosure-jwt/issues/327
>
> - https://github.com/oauth-wg/oauth-selective-disclosure-jwt/issues/345
>
>
>
> Those issues don't really address the point.
>
>
>
> Per RFC 8725: JSON Web Token Best Current Practices (rfc-editor.org)
> <https://www.rfc-editor.org/rfc/rfc8725.html#name-use-explicit-typing> --
> the best practice would be to have a single type that would allow a library
> to know it is an SD-JWT. If additional context is needed, perhaps that
> should be a different header property?
>