Storage Constrained Information Theoretic Symmetric Private Information Retrieval

Abstract

Private information retrieval (PIR) is an important protocol in cryptographic community to ensure privacy of the user when retrieving information from untrusted databases. In a variation to this problem, symmetric private information retrieval (SPIR) is a protocol which ensures the privacy of user as well as databases. A major drawback for the majority of existing works on information theoretic PIR and SPIR is that they focus on scenarios where all databases store the entire data set (i.e. replicated databases). The goal of this thesis is to present PIR and SPIR schemes for storage constrained databases. For both PIR and SPIR, we present a systematic approach to utilize storage constrained databases. The technical contribution involves two main parts: (a) a careful storage scheme to split and store messages across databases; and (b) construction of information theoretic PIR and SPIR schemes from such databases. We also compare our results to the fully replicated scenario, as well as compare the differences between the communication overhead of PIR and SPIR schemes.