Consider a user A who wishes to download the mp3 file with the title T. Server B has the file. Our goal is to develop a system which allows A to download file from B so that no single network entity knows identity of both A and B. A mixed network (e.g. TOR) as well as a directory service is at your disposal.
Describe how B is able to register anonymously at directory service (letting the service know that it has title T) such that A may use the directory service to receive the file from B. Note that directory service does NOT take part in the file transfer.