W3C home > Mailing lists > Public > public-credentials@w3.org > October 2020

Re: using PDFs as a VC container...

From: Orie Steele <orie@transmute.industries>
Date: Tue, 20 Oct 2020 10:52:29 -0500
Message-ID: <CAN8C-_KDJcd67GGg1k7=dFFvULXu-63V4Bnu-_p=iMGhfd9azg@mail.gmail.com>
To: Kostas Karasavvas <kkarasavvas@gmail.com>
Cc: Credentials Community Group <public-credentials@w3.org>
This is awesome!

Regarding revocation, see:

- https://github.com/digitalbazaar/vc-revocation-list
- https://w3c-ccg.github.io/vc-status-rl-2020/

Here is an example, using did:web
https://did.actor/#alice-didwebdidactoralice

I have experimented with generating DIDs and VCs as pdfs...

Using data matrix / compressed qr codes so they can also be converted back
and forth to paper.

I've been waiting for CBOR-LD to mature, since the compression of VCs is
one of the major limiting factors for QR Code based transports.

I imagine this would also help with storing the data in pdf files as well.

Regards,

OS


On Tue, Oct 20, 2020 at 10:42 AM Kostas Karasavvas <kkarasavvas@gmail.com>
wrote:

>
> Hi all!
>
> I would like to introduce the work that I have been involved with. I have
> been following the list/group for a while now and want to try to find the
> time to be more active   ... that, plus Leonard's presentation was a great
> opportunity/introduction :-)
>
> TL;DR:
> We have been using PDFs as a credentials' container and anchoring the
> document hashes on the blockchain. A blockchain proof (chainpointv2) is
> added in the PDF metadata which results in self-contained and
> self-verifiable PDF documents; the PDF is the only thing needed to view the
> credential and validate the credential*. There are open source validators
> that are trivial to use and/or host.
>
> The longer version:
> The University of Nicosia has been anchoring/issuing credentials (PDFs)
> for some of their courses on the Bitcoin blockchain since 2014. Back then
> the process was more manual/adhoc. In 2016 the solution was re-designed to
> (more or less) what we have today:
>
> - several PDFs are hashed and merklized, merkle root is anchored in the
> blockchain (bitcoin is used but it is blockchain agnostic)
> - merkle proofs, txid, etc. are stored in the respective PDF's metadata
> (using json format)
> - PDFs can be disseminated/stored as they always were
>
> Several companies already use PDFs so our solution fits into their
> workflows seamlessly. They had PDFs, they are anchored, and they still have
> PDFs**.
>
> A meta-protocol was designed to encode the data stored in the blockchain
> in a way that allows on-chain issuing/validation and revocation of the
> credentials. The process is described in detail in:
> https://ieeexplore.ieee.org/document/8525400
> (I can share if requested... not sure if the above is accessible to all)
>
> An open source implementation (with tools) can be found at:
> https://github.com/verifiable-pdfs/blockchain-certificates
> Validators at: https://github.com/verifiable-pdfs/validator-widget  and
> https://github.com/verifiable-pdfs/blockchain-certificates-validation
>
> From 2017 all of the credentials and diplomas issued by the University are
> issued using this platform. From 2019 the solution was commercialized
> (Block.co) to make it easier for potential clients (abstracting blockchain
> infrastructure, etc.). Several more clients/use cases came up rather than
> only educational credentials.
>
> We have looked into this in the past but it was frozen. Now we are again
> in the process of preparing/designing for VC-compatibility. We already use
> json format so using the VC format would be straight-forward in itself.
>
> However, I seem to be missing some parts, like how to formally define
> revocation mechanisms or how to formally include the blockchain proof. Is
> there a place where we can define our issuing / revocation mechanism so it
> can be reused/interoperable?
>
> Also it would be of great interest to see how we can properly use XMP that
> Leonard mentioned in a more standardized way in our solution.
>
> I would be happy to discuss further with anyone interested and thank you
> all for your time reading this.
>
> Regards,
> Kostas
>
> * Not unlike VCs other than the fact that the 'presentation'-layer is the
> verifiable container itself.
> ** The solution can apply to any file that supports custom metadata.
>
> --
> Konstantinos A. Karasavvas
> Software Architect, Blockchain Engineer, Researcher, Educator
> https://twitter.com/kkarasavvas
>
>

-- 
*ORIE STEELE*
Chief Technical Officer
www.transmute.industries

<https://www.transmute.industries>
Received on Tuesday, 20 October 2020 15:52:54 UTC

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