Re: C2PA Specifications - First Public Draft

Steven – not sure how you see C2PA manifests and DID documents being similar.

A C2PA manifest is an entity designed to be embedded into an asset (image, video, document, etc.) and fully functional when offline (though, of course, there are also opportunities/improvements that can exist when online).  A DID document, on the other hand, is an entity returned by a service based on the resolution of its DID method and so required to work only when online.

You are correct that in C2PA we view DIDs as an identifier to what we define as an actor – which could be a human, a machine, an organization, etc. Since we desire to support offline usage, the DID could be resolved ahead of time (to a VC) and then the VC included into the manifest as described in the specification. For DID documents that don’t return VC’s, you rightly point out that we don’t have a solution at this time – and I would welcome discussions with you and others about what sorts of use cases you envision and how we could support them.

You are also correct that C2PA does not mandate VC’s nor DIDs – and that is also by design.  We do believe that both are important technologies in the future of identity and we wanted to ensure that they are first class citizens in the system (hence the reasons that VCs get their own separate storage area in our manifest!).  However, at this time, they aren’t adopted widely enough to be something that we could mandate and have our specification see the levels of adoption that we require.  So support for other forms of identity, credentialling, etc. also needs to be provided for.  And in that way, we are aligned with the work of Schema.org – which is also why we have made it a first class citizen.

Leonard

From: Steven Rowat <steven_rowat@sunshine.net>
Date: Thursday, September 2, 2021 at 12:13 PM
To: Leonard Rosenthol <lrosenth@adobe.com>, public-credentials (public-credentials@w3.org) <public-credentials@w3.org>
Subject: Re: C2PA Specifications - First Public Draft
On 2021-09-01 6:08 am, Leonard Rosenthol wrote:

I’ve been mentioning the work of the Coalition for Content Provenance and Authenticity (C2PA) for a while now, including our usage of W3C Verifiable Credentials.  I am excited to announce that the first public draft of our specification is available for review and comment.  I would welcome the input from this community on how we have chosen to integrate VC’s into our system.

[snip]...

The draft specification can be accessed through the C2PA website<https://c2pa.org/public-draft/><https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fc2pa.org%2Fpublic-draft%2F&data=04%7C01%7Clrosenth%40adobe.com%7C5a74c69ef2604aaf148e08d96e2ca18e%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C0%7C637661960234430686%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=HKh%2BmyM9ZL9rCTaCZkPmNUR0%2BG14at3FK1668dRZDgk%3D&reserved=0>, and comments will be accepted through a web submission form<https://docs.google.com/forms/d/e/1FAIpQLSevOsvZKHIc_4Dljk7IkoW37mcuItUEV3I6hoUZhR2suxRVPg/viewform><https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fdocs.google.com%2Fforms%2Fd%2Fe%2F1FAIpQLSevOsvZKHIc_4Dljk7IkoW37mcuItUEV3I6hoUZhR2suxRVPg%2Fviewform&data=04%7C01%7Clrosenth%40adobe.com%7C5a74c69ef2604aaf148e08d96e2ca18e%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C0%7C637661960234440657%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=H1q05OZ2LrXP43w5d%2FC6Ap795xiYPNAfs8ZMZAOBpvQ%3D&reserved=0> and GitHub<https://github.com/c2pa-org/public-draft><https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fgithub.com%2Fc2pa-org%2Fpublic-draft&data=04%7C01%7Clrosenth%40adobe.com%7C5a74c69ef2604aaf148e08d96e2ca18e%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C0%7C637661960234440657%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=wlMhxgxtAVRXhbKyV%2B%2F%2BKnoD9c7U6P0mwmwqk70bNx4%3D&reserved=0> until November 30, 2021.

Leonard,

C2PA seems like a very interesting and ambitious project. But after scanning through, my take is that it recreates something like DID Documents. In other words that it's a parallel project that performs the same function, not an extension into new function. Am I off base here, or is this true, in your opinion?

I note that you only use DIDs a single time, in section 7.1, the Verifiable Credential example. And then right away you specifically note about this that DIDs are not necessary for VCs:

"Although the example above and many examples in the W3C Verifiable Credentials data model specification use Decentralized Identifiers (DIDs) as the value of the id field, DIDs are not necessary for W3C Verifiable Credentials to be useful. Specifically, W3C Verifiable Credentials do not depend on DIDs and DIDs do not depend on W3C Verifiable Credentials. DID-based URLs are just one way to express identifiers associated with subjects, issuers, holders, credential status lists, cryptographic keys, and other machine-readable information associated with a W3C Verifiable Credential."

And that's the only place in this whole, very large, specification, that DIDs appear. And VCs themselves, you indicate, are a tolerated add-on, but not necessary either for your system (as far as I can determine).

So:

On a continuum of possibility, I'll ask whether you think the C2PA project is *closer* to aiming for...

1. Integrating with DID based provenance systems, so that there can be interoperability with DID published data (and formal DID Documents).

or

2. Creating a document provenance system that has no need for DIDs, so that DIDs will be unnecessary and die out, and the functions they're aiming for replaced by the C2PA system?



Steven Rowat











C2PA is accepting new members. To join, visit https://c2pa.org/membership/<https://nam04.safelinks.protection.outlook.com/?url=https%3A%2F%2Fc2pa.org%2Fmembership%2F&data=04%7C01%7Clrosenth%40adobe.com%7C5a74c69ef2604aaf148e08d96e2ca18e%7Cfa7b1b5a7b34438794aed2c178decee1%7C0%7C0%7C637661960234450608%7CUnknown%7CTWFpbGZsb3d8eyJWIjoiMC4wLjAwMDAiLCJQIjoiV2luMzIiLCJBTiI6Ik1haWwiLCJXVCI6Mn0%3D%7C1000&sdata=KK43oM%2FJrgjUpfMR9057bCLq72KOhkpiBMSrMLBAEwQ%3D&reserved=0>.



About C2PA

The Coalition for Content Provenance and Authenticity (C2PA) is an open, technical standards body addressing the prevalence of misleading information online through the development of technical standards for certifying the source and history (or provenance) of media content. C2PA is a Joint Development Foundation project, formed through an alliance between Adobe, Arm, BBC, Intel, Microsoft and Truepic. For more information, visit c2pa.org.



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