[jose] Re: Do you need the JWP JSON Serialization?

[Neil Madden <[e-mail]>]

Maybe I’m missing something, but all of the disclosures are covered by the SD-JWT signature and so (a) are protected, and are (b) immutable.

— Neil

> On 8 Aug 2024, at 19:18, Orie Steele <[e-mail]> wrote:
> 
> That's fair : )
> 
> Let's replace "suspicion" with "I would have argued for a different design".
> 
> In JOSE, ~ is just used as a placeholder for "missing unprotected header".
> 
> You still need to validate that the correct mutable data was included, and that no "unexpected mutable data" was included.
> 
> That's a "verifier policy over mutable data".
> 
> In the context of SD-JWT that means checking disclosures, matching their hash to the kbt and making sure the kbt is signed by the cnf.
> 
> That is very similar to the kind of unprotected header processing that COSE supports, see:
> 
> https://www.rfc-editor.org/rfc/rfc9338.html#section-2 <https://www.rfc-editor.org/rfc/rfc9338.html#section-2>
> 
> Sure maybe it's less obvious that jwt (cnf) -> disclosures -> hash -> kbt signed by cnf is a kind of counter signature.
> 
> But it is a second signature, over a specific set of disclosures that is grouped together with the first signature, which are verified together.
> 
> https://datatracker.ietf.org/doc/html/draft-ietf-oauth-selective-disclosure-jwt-10#section-9.1 <https://datatracker.ietf.org/doc/html/draft-ietf-oauth-selective-disclosure-jwt-10#section-9.1>
> 
> """
> Unprotected headers other than disclosures are not covered by the digest, and therefore, as usual, are not protected against tampering.
> """
> 
> This is similar to how values in unprotected headers in COSE are not protected, unless there is some "verification process" such as checking a counter signature, or merkle tree inclusion proof.
> 
> Isn't JWP meant to replace SD-JWT in some cases that require stronger unlinkability?
> 
> IIRC SD-JWT and OAUTH had good reasons to define a JSON Serialization, and if it's used, those users should be able to switch to JWP or CWP in the future.
> 
> OS
> 
> 
> 
> 
> 
> On Thu, Aug 8, 2024 at 12:33 PM Brian Campbell <[e-mail] <mailto:[e-mail]>> wrote:
> 
> 
> On Thu, Aug 8, 2024 at 11:27 AM Orie Steele <[e-mail]> wrote:
>  <snip>
> 
> If JWTs had unprotected headers, I suspect SD-JWT would have used them for the mutable part (disclosures).
> 
> That suspicion is entirely incorrect. 
>  
> <snip>
> 
> 
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> -- 
> 
> ORIE STEELE
> Chief Technology Officer
> www.transmute.industries <http://www.transmute.industries/>
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