More is Less: Perfectly Secure Oblivious Algorithms in the Multi-Server Setting

TL;DR

This paper introduces a perfectly secure 3-server ORAM scheme that surpasses single-server schemes in efficiency, demonstrating that multiple servers can overcome known limitations and achieve better security and performance.

Contribution

The paper presents the first 3-server ORAM scheme with perfect security that outperforms single-server schemes and shows multiple servers can surpass single-server lower bounds.

Findings

3-server ORAM scheme outperforms single-server by a logarithmic factor

Multiple servers can overcome known single-server lower bounds

First demonstration of multi-server advantage in specific algorithms

Abstract

The problem of Oblivious RAM (ORAM) has traditionally been studied in a single-server setting, but more recently the multi-server setting has also been considered. Yet it is still unclear whether the multi-server setting has any inherent advantages, e.g., whether the multi-server setting can be used to achieve stronger security goals or provably better efficiency than is possible in the single-server case. In this work, we construct a perfectly secure 3-server ORAM scheme that outperforms the best known single-server scheme by a logarithmic factor. In the process, we also show, for the first time, that there exist specific algorithms for which multiple servers can overcome known lower bounds in the single-server setting.