[DvdGiessen]

You might also be interested in the IRMA protocol and the app implementing it, Yivi. They support a similar scheme, but using some additional cryptographic systems that provide extra security properties such as unlinkability that are very useful for privacy.

https://docs.yivi.app/technical-overview/

Since I learned about it I've been hoping a system providing such unlinkability would be further developed and preferably adopted as the standard for online identity by for example the EU. Unfortunately I don't think the current proposals for the eIDAS include this (although it's been a while since I read up on this and I'd love to hear from someone more familiar if I'm wrong!)