[OID4VCI] align credential format identifiers with media types

[OIDF-automation]

Imported from AB/Connect bitbucket: https://bitbucket.org/openid/connect/issues/1960

Original Reporter: authlete-taka

How about changing the following credential format identifiers:

• jwt_vc_json
• jwt_vc_json-ld

to media types like below?

• vc+jwt
• vc+ld+jwt

References:

• Securing Verifiable Credentials using JSON Web Tokens
• Media Types with Multiple Suffixes

Likewise, I feel that SD-JWT based VC should be given the format identifier vc+sd+jwt (instead of vc+sd_jwt).

[OIDF-automation]

Imported from AB/Connect bitbucket - Original Commenter: authlete-taka

Sorry, regarding SD-JWT VC. “SD-JWT-based Verifiable Credentials with JSON payloads (SD-JWT VC)” defines the media type vc+sd-jwt, and if the intention of sd-jwt is to mean the “combined format” (<JWT>~<Disclosure>~...), sd-jwt should not be changed to sd+jwt.

[OIDF-automation]

Imported from AB/Connect bitbucket - Original Commenter: KristinaYasuda

good point. I am in general in support of moving towards using media types like you are suggesting.

Based on the development of SD-JWT-based Verifiable Credentials (SD-JWT VC) (vcstuff.github.io), I think jwt_vc_json 's identifier would be vc+sd-jwt too.

We had a lengthy discussion at the last IETF and we agreed that `+sd-jwt` is more suitable because the point of having +sd-jwt is to clearly differentiate processing rules etc from +jwt.

[OIDF-automation]

Imported from AB/Connect bitbucket - Original Commenter: KristinaYasuda

duplicate of #24 .

[Sakurann]

what would be the media type for ldp_vc? I think media types defined in w3c vc+jwt and vc+ld+jwt were intended to talk about an (unsigned) payload...