Path ORAM: An Extremely Simple Oblivious RAM Protocol

TL;DR

Path ORAM is a simple, practical Oblivious RAM protocol with low client storage and logarithmic bandwidth overhead, making it suitable for secure processor design.

Contribution

It introduces Path ORAM, the simplest and most practical ORAM scheme with formal proofs of efficiency and widespread adoption in secure hardware.

Findings

Achieves O(log N) bandwidth cost for blocks of size Omega(log^2 N) bits

Outperforms previous small-client-storage ORAM schemes asymptotically

Has been adopted in secure processor architectures

Abstract

We present Path ORAM, an extremely simple Oblivious RAM protocol with a small amount of client storage. Partly due to its simplicity, Path ORAM is the most practical ORAM scheme known to date with small client storage. We formally prove that Path ORAM has a O(log N) bandwidth cost for blocks of size B = Omega(log^2 N) bits. For such block sizes, Path ORAM is asymptotically better than the best known ORAM schemes with small client storage. Due to its practicality, Path ORAM has been adopted in the design of secure processors since its proposal.