The rise of the Franken-standards (SD-JWT VC DM)

👋 Dear NGI Community

In my previous articles (here and here and here), I shared some thoughts about the complex landscape of technical standards in the field of digital identity, especially related to the EU Digital Identity Wallet.

One example of competing standards that I find especially interesting is that of credential formats, i.e. the technical formats of the digital documents in your wallet that prove something about you. On one hand, there is the Verifiable Credential Data Model (VCDM), and on the other hand, there is SD-JWT VC. There is currently much confusion surrounding these two technologies, starting with their names:

✅ The term "Verifiable Credential (VC)" was first introduced by the Verifiable Credential Data Model (VCDM) specification and became very successful and well-known.

✅ The community around SD-JWT VC adopted and overloaded the name due to its popularity and recognition on the market, but the two specifications have diverged so much by now that they are basically completely incompatible, despite what the similar names might suggest.

Unless you are a deep insider of the standardization processes and the politics surrounding them, it is very hard to understand why such multiple technical specifications exist that basically fulfill the same purpose, yet are incompatible.

The logical consequence of this will be non-existent interoperability between different use cases and ecosystems. Various misunderstandings and incorrect information are being spread about the different technologies, which leads to further confusion. The standardization processes also become harder due to potential ambiguity about credential formats.

This divergence also causes problems in concrete practical applications. For example, there are digital identity use cases in the education field that require the use of a vocabulary known as European Learning Model (ELM), but this only works with the Verifiable Credential Data Model (VCDM), not with SD-JWT VC. This and similar situations create pressure to somehow resolve the diverging landscape of credential formats. This pressure has now resulted in a new proposal known as SD-JWT VC DM, which promises to combine the "best of both worlds".

This sounds good in theory, however in practice, that proposed format is a Frankenstein's monster-like mix of building blocks taken from different specifications, and combined in strange ways that don't really fit together. This results in even more complexity, instead of converging or resolving anything.

Since both the Verifiable Credential Data Model (VCDM) and SD-JWT VC are based on very different data models, it is completely unclear how a combination of both would work and be processed. In fact, when evaluating the examples provided by the SD-JWT VC DM proposal, it becomes clear that those examples are actually compliant with NEITHER of the two credential formats, despite the promises of those advocating for this "combined" format.

What's even worse is that work on SD-JWT VC DM is primarily happening in private Signal channels and in closed standardization groups.

🔥There is virtually no transparency and no way to gain insight into the development of this technology.🔥

People working on it hide their identities by using temporary Github accounts. Questions about this work do not get answered. Even large EU-funded projects such as EBSI-VECTOR and TRACE4EU that are supposed to deploy digital identity use cases are unable to obtain useful information about SD-JWT VC DM.

To summarize, SD-JWT VC DM is an effort that is mostly hidden from the general public, and the information that is currently available contains a number of nice-sounding claims and promises which simply do not hold true on the technical level. In its current form, this will lead to further divergence instead of "uniting two worlds".

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