I convened the session “What does Presentation Exchange do and what parts of it do we actually need?” this week at the Internet Identity Workshop (IIW) to continue the discussion started during two unconference sessions at the 2023 OAuth Security Workshop. I briefly summarized the discussions that occurred at OSW, then we had a vigorous discussion of our own.
Key points made were:
- There appeared to be rough consensus in the room that Presentation Exchange (PE) is pretty complicated. People had differing opinions on whether the complexity is worth it.
- A lot of the complexity of PE comes from being able to request multiple credentials at once and to express alternatives.
- Ultimately, the verifier knows what kinds of credentials it needs and the relationships between them. PE tries to let the verifier express some of that to the wallet.
- Code running in the verifier making choices about the credentials it needs will always be more powerful than PE, because it has the full decision-making facilities of programming languages – including loops, conditionals, etc.
- Making a composite request for multiple credentials can have a better UX than a sequence of requests. In some situations, the sequence could result in the person having to scan multiple QR codes. There may be ways to avoid that, while still having a sequence of requests.
- Some said that they need the ability to request multiple credentials at once.
- Brent Zundel (a PE author) suggested that while wallets could implement all of PE, verifiers could implement only the parts they need.
- Not many parties had implemented all of PE. Torsten Lodderstedt suggested that we need feedback from developers.
- We could create a profile of PE, reducing what implementers have to build and correspondingly reducing its expressive power.
Thanks to everyone who participated for an informative and useful discussion. My goal was to help inform the profiling and deployment choices ahead of us.
P.S. Since Thursday’s discussion, it occurred to me that a question I wish I’d asked is:
- When a verifier needs multiple credentials, they may be in different wallets. If the verifier tries to make a PE request for multiple credentials that are spread between wallets, will it always fail because no single wallet can satisfy it?
Fodder for the next discussion…