PROTECTING PRIVACY AND SECURING DATABASES WITH QUANTUM NETWORKS

Abstract

We investigate information-theoretic (IT) secure three-party symmetric private information retrieval (SPIR) protocols, which provide user and data privacy when a user retrieves an entry from a database. We propose the use of a quantum key distribution (QKD) network to supply the necessary IT-secure symmetric keys for the first IT-secure implementation of a two-database SPIR. This is demonstrated experimentally on a fingerprint database using a measurement-device-independent (MDI) QKD setup. To further enhance efficiency, a high-speed receiver-device-independent (RDI) QKD implementation is proposed, and the security of the protocol against coherent attacks is established. A new two-user quantum SPIR protocol is also proposed, which capitalises on the local operation and classical communication (LOCC) between the two users. While the implementation of the proposed protocol could be challenging, it has strong theoretical interests as there is no classical equivalent and could lead to new forms of quantum advantage in SPIR.