GigaDORAM: Breaking the Billion Address Barrier

We design and implement GigaDORAM, a novel 3-server Distributed Oblivious Random Access Memory (DORAM) protocol. Oblivious RAM allows a client to read and write to memory on an untrusted server, while ensuring the server itself learns nothing about the client's access pattern. Distributed Oblivious RAM (DORAM) allows a group of servers to efficiently access a secret-shared array at a secret-shared index. A recent generation of DORAM implementations (e.g. FLORAM, DuORAM) has focused on building DORAM protocols based on Function Secret-Sharing (FSS). These protocols have low communication complexity and low round complexity but linear computational complexity of the servers. Thus, they work for moderate-size databases, but at a certain size, these FSS-based protocols become computationally inefficient. In this work, we introduce GigaDORAM, a hierarchicalsolution-based DORAM featuring poly-logarithmic computation and communication, but with an over 100× reduction in rounds per query compared to previous hierarchical DORAM protocols. In our implementation, we show that for moderate to large databases where FSS-based solutions become computation bound, our protocol is orders of magnitude more efficient than the best existing DORAM protocols. When N = 2 31 , our DORAM is able to perform over 700 queries per second.