Improved Storage for Efficient Private Information Retrieval
Abstract
We consider the problem of private information retrieval from $N$ \emph{storageconstrained} databases. In this problem, a user wishes to retrieve a single message out of $M$ messages (of size $L$) without revealing any information about the identity of the message to individual databases. Each database stores $\mu ML$ symbols, i.e., a $\mu$ fraction of the entire library, where $\frac{1}{N} \leq \mu \leq 1$. Our goal is to characterize the optimal tradeoff curve for the storage cost (captured by $\mu$) and the normalized download cost ($D/L$). We show that the download cost can be reduced by employing a hybrid storage scheme that combines \emph{MDS coding} ideas with \emph{uncoded partial replication} ideas. When there is no coding, our scheme reduces to AttiaKumarTandon storage scheme, which was initially introduced by MaddahAliNiesen in the context of the caching problem, and when there is no uncoded partial replication, our scheme reduces to BanawanUlukus storage scheme; in general, our scheme outperforms both.
 Publication:

arXiv eprints
 Pub Date:
 August 2019
 arXiv:
 arXiv:1908.11366
 Bibcode:
 2019arXiv190811366B
 Keywords:

 Computer Science  Information Theory;
 Computer Science  Cryptography and Security;
 Computer Science  Databases
 EPrint:
 ITW 2019