Earlier quoted context omitted.
You can verify who someone is without knowing specifically who "who" refers to. We do it all the time. I give a one-time code to service X and it knows I am who I say I am, but the code I gave is virtually worthless information. All it knows is that I have credentials, and I am the authorized person to have those credentials because I have physical access to some device, unknown, which is known to belong to said pers…
You're omitting the part where you have to disclose who you are to the party issuing the credential. If they issue you a unique credential while knowing your identity then they can trace back all your uses of it to your identity. When that party is the government or within the government's jurisdiction, the government has the capacity to do that even if the services where you use the credential are operated by a thir…
A blind signature could be used to have the ID checking party sign the credential without seeing it.