Oblivious Paxos: Privacy-Preserving Consensus Over Secret-Shares

State-of-the-art consensus protocols like Paxos reveal the values being agreed upon to all nodes, but some deployment scenarios involving a subset of nodes outsourced to public cloud providers motivate hiding the value. In this work, we present the primary-backup secret-shared state machine (PBSSM) architecture and an underlying consensus protocol Oblivious Paxos (OPaxos) that enable strong consistency, high availability, privacy, and fast common-case performance. OPaxos enables privacy-preserving consensus by allowing acceptors to safely agree on a secret-shared value without utrusted acceptors knowing the value. We also present Fast Oblivious Paxos (Fast-OPaxos), which enables consensus over secret-shares in three one-way delays under low concurrency settings. Our prototype-driven microbenchmarks and smarthome case study show that OPaxos induces a negligible latency overhead of at most 0.1 ms compared to Paxos while maintaining more than 85% of Paxos' capacity for small requests, and can provide lower latency and higher capacity compared to Paxos for large request sizes.