The Capacity of Single-Server Weakly-Private Information Retrieval

A private information retrieval (PIR) protocol guarantees that a user can privately retrieve files stored in database without revealing any about the identity of requested file. Existing information-theoretic PIR protocols ensure perfect privacy, i.e., zero leakage to servers storing database, but at cost high download. In this work, we present weakly-private (WPIR) schemes trade off privacy improve download when is on single server. We study tradeoff between and terms mutual (MI) maximal (MaxL) metrics. By relating WPIR problem rate-distortion theory, download-leakage function, which defined as minimum required all single-server for given level fixed file size, introduced. characterizing function MI MaxL metrics, capacity fully described.