Re: Questions regarding VC 2.0 document

For multiple proof, another use case would be to have 2 signatures, each
allowing different cryptographic features such as zkp/selective disclosure.

On Tue, Oct 24, 2023 at 11:21 AM Dmitri Zagidulin <dzagidulin@gmail.com>
wrote:

> Hi Stephanie, great questions.
>
> 1. (re JSON-LD) So, the main value proposition to JSON-LD is basically
> extensibility. What do I mean by that? It allows your JSON objects to have
> property names that are globally unique (because they're URLs). And also,
> in the best case, each property is self-documenting (a developer can go to
> that URL and see exactly what was meant by that field). (I talk about this
> in my blog post, Understanding Linked Data.
> <https://medium.com/@codenamedmitri/understanding-linked-data-91b31ba544ec>
> )
> And why is extensibility important? Because VC 2.0 is just the data model
> for the credential /envelope/, most implementers will need to come up with
> their own VC payloads (define new credential types). And there's only two
> basic mechanisms to do that in an interoperable fashion -- you can register
> the types and claims in a central registry somewhere. Or you can create and
> publish a @context, which essentially serves as a decentralized namespace
> and registry.
>
> You mentioned that one of the benefits might be preserving the data
> structure. That's more the domain of JSON Schemas (see the Data Schemas
> <https://w3c.github.io/vc-data-model/#data-schemas> section of the VC DM
> 2.0 spec), and it makes a lot of sense to use both JSON Schemas and JSON-LD @contexts
> together.
> Incidentally.
>
> The other main benefit to JSON-LD with regards to VCs specifically, is
> that it enables you to deterministically convert the VC between JSON, CBOR,
> YAML etc formats, while the signature remains the same. (This is not a very
> common requirement or use case -- usually done for compression reasons, but
> I thought I'd mention it).
>
> 2. (multiple proofs) There are a couple of reasons to include multiple
> proofs.
> One is, multi-signature scenarios. (Meaning, multiple parties need to sign
> the VC, either using threshold signatures (N of M, etc), or just "everyone
> in the C-Suite has signed this important VC representing a company
> decision" kind of things).
>
> And the other is - key formats. For example, if you're an issuer, and you
> know that one of your intended consumer audiences only supports Ed25519
> type keys, but another consumer only supports RSA keys, then you can create
> two signatures -- one with your RSA key and one with your Ed25519 key, so
> that both parties can verify easily.
>
> Dmitri
>
>
> On Tue, Oct 24, 2023 at 6:04 AM ステファニー タン（SBIホールディングス） <
> tstefan@sbigroup.co.jp> wrote:
>
>> Hi, we have questions about some items in the VC 2.0 document (21 october
>> 2023 version)
>>
>>    1. We assume that one good reason to use JSON-LD is the ability to be
>>    able to preserve data structure by using @context. Are there other reasons?
>>    2. In Example 17（
>>    https://www.w3.org/TR/vc-data-model-2.0/#example-basic-structure-of-a-presentation）,
>>    it appears that we can include more than 1 proof. We would like to ask the
>>    reason for this decision?
>>
>>
>> Thank you for any advice!
>>
>> Best regards,
>> Stefannie Tan
>>
>