What is the formal name -- and description -- of the problem of giving users access to a resource exactly once each while not requiring them to identify themselves?
In other words, to have a system that is able to give away access tokens to users as long as they have never obtained any before.
Assuming that users are able to perform cryptographic functions, and can be assumed to have personal certificates signed by the system, but which they do not want to reveal to the system in order to gain access.
Is there such a model? Is there such a well-described problem?