A t-private private information retrieval (PIR) scheme allows a user to retrieve the ith bit of an n-bit string x replicated among k servers, while any coalition of up to t servers learns no information about i. We present a new geometric approach to PIR, and obtain
A t-private k-server protocol with communication 0(\frac{{k^2 }}{t}\log kn^{{1 \mathord{\left/ {\vphantom {1 {\left\lfloor {(2k - 1)/t} \right\rfloor }}} \right. \kern-\nulldelimiterspace} {\left\lfloor {(2k - 1)/t} \right\rfloor }}}), removing the (\begin{array}{*{20}c}k \\t \\\end{array}) term of previous schemes. This answers an open question of [14]. A 2-server protocol with O(n^1/3) communication, polynomial preprocessing, and online work O(n/ log^r n) for any constant r. This improves the O(n/ log^2 n) work of [8]. Smaller communication for instance hiding [3, 14], PIR with a polylogarithmic number of servers, robust PIR [9], and PIR with fixed answer sizes [4]. To illustrate the power of our approach, we also give alternative, geometric proofs of some of the best 1-private upper bounds from [7].