On query self-submission in peer-to-peer user-private information retrieval

User-private information retrieval (UPIR) is the art of retrieving information without telling the information holder who you are. UPIR is sometimes called anonymous keyword search. This article discusses a UPIR protocol in which the users form a peer-to-peer network over which they collaborate in protecting the privacy of each other. The protocol is known as P2P UPIR. It will be explained why the P2P UPIR protocol may have a flaw in the protection of the privacy of the client in front of the server. Two alternative variations of the protocols are discussed. One of these will prove to resolve the privacy flaw discovered in the original protocol. Hence the aim of this article is to propose a modification of the P2P UPIR protocol. It is justified why the projective planes are still the optimal configurations for P2P UPIR for the modified protocol.