Blurry-ORAM: A Multi-Client Oblivious Storage Architecture

Since the development of tree-based Oblivious RAM by Shi et al. (Asiacrypt ’11) it has become apparent that privacy preserving outsourced storage can be practical. Although most current constructions follow a client-server model, in many applications it is desirable to share data between different clients, in a way that hides the access patterns, not only from the server, but also between the clients. In this work, we introduce BlurryORAM, an extension of Path-ORAM that allows for oblivious sharing of data in the multi-client setting, so that accesses can be hidden from the server and other clients. Our construction follows the design of Path-ORAM as closely as possible in order to benefit from its performance as well as security. We prove our construction secure in a setting where the clients are semi-honest, do not trust each other but try to learn the access patterns of each other.