Can you prove your Internet Identity to another service?

Imagine this usecase:

  • the user has II created and logins to some service A;
  • service A attaches some data to the user’s II (some rating metrics for example);
  • now the user logins with the same II to some other service B;
  • service B wants to check if the users rating on service A is 10 out of 10 and provide some additional functionality if it so.

How do I implement such a pattern, while services are unable to link two separate principals of this user, despite them being connected to the same single II?

Should service A ask for users Identity Number (this short Id unique for each II) and attach it’s data to this number, so service B then could also ask for this Identity Number and check the data left by service A?

Thanks in advance!

The Internet Identity service doesn’t provide that; it really tries hard to maintain the privacy properties of the per service pseudonyms.

So you’d need to build such a feature into service A and B, probably using some back-and-forth between the frontends of the services, maybe even asking the user for permission.