Towards Doubly Efficient Private Information Retrieval.

Private Information Retrieval (PIR) allows a client to obtain data from a public database without disclosing the locations accessed. Traditionally, the stress is on preserving sublinear work for the client, while the server’s work is taken to inevitably be at least linear in the database size. Beimel, Ishai and Malkin (JoC 2004) show PIR schemes where, following a linear-work preprocessing stage, the server’s work per query is sublinear in the database size. However, that work only addresses the case of multiple non-colluding servers; the existence of single-server PIR with sublinear server work remained unaddressed.