Mitigating Cryptographic Bottlenecks of Low-Latency BFT Protocols

Mitigating Cryptographic Bottlenecks of Low-Latency BFT Protocols

연구 분야: Networking

학회: IFIP International Conference on Distributed Applications and Interoperable Systems

Byzantine fault-tolerant protocols enable applications to run even in the presence of arbitrary faults. Unfortunately, to reach a consensus on the order to execute client requests, these protocols perform costly cryptographic operations that limit their performance. This hinders their adoption for latency-sensitive applications executed in data-centres, such as fault-tolerant machine learning or finance applications. We propose two mechanisms to reduce the impact of digital signature verification: Speculative Execution to decouple consensus from the verification of the digital signature of protocol messages; and Secure Request Broadcast where replicas do not need to wait for the primary before they can verify a request signature. Both mechanisms are combined with a Blocklisting mechanism to ensure robustness against attacks. We implement both mechanisms in SPECULOR, a PBFT-based BFT protocol tailored for a relaxed fault model where clients do not crash and periodically retransmit their requests. Our evaluation shows SPECULOR reduces the tail-latency by at least 34% compared to PBFT while maintaining robustness under attacks. Finally, we discuss future modifications in order to apply this design to a wide range of BFT protocols under traditional assumptions.