Extended Combinatorial Constructions for Peer-to-peer User-Private Information Retrieval

TL;DR

This paper enhances peer-to-peer user-private information retrieval schemes by introducing generalized combinatorial designs, analyzing privacy trade-offs, and proposing protocols that balance dynamic user participation with privacy against other users.

Contribution

It extends existing P2P UPIR schemes using more general combinatorial designs, clarifies privacy goals, and introduces new protocols with flexible privacy and dynamic user features.

Findings

New attack identified on existing schemes

Protocols using general designs improve flexibility

Trade-offs between user privacy and system dynamics analyzed

Abstract

We consider user-private information retrieval (UPIR), an interesting alternative to private information retrieval (PIR) introduced by Domingo-Ferrer et al. In UPIR, the database knows which records have been retrieved, but does not know the identity of the query issuer. The goal of UPIR is to disguise user profiles from the database. Domingo-Ferrer et al.\ focus on using a peer-to-peer community to construct a UPIR scheme, which we term P2P UPIR. In this paper, we establish a strengthened model for P2P UPIR and clarify the privacy goals of such schemes using standard terminology from the field of privacy research. In particular, we argue that any solution providing privacy against the database should attempt to minimize any corresponding loss of privacy against other users. We give an analysis of existing schemes, including a new attack by the database. Finally, we introduce and analyze two new protocols. Whereas previous work focuses on a special type of combinatorial design known as a configuration, our protocols make use of more general designs. This allows for flexibility in protocol set-up, allowing for a choice between having a dynamic scheme (in which users are permitted to enter and leave the system), or providing increased privacy against other users.