Strengthened Fault Tolerance in Byzantine Fault Tolerant Replication
This work provides improved fault tolerance for permissioned blockchain systems, which is crucial for their security and reliability, especially for systems that need to withstand a higher proportion of malicious actors.
This paper introduces Strengthened Fault Tolerance (SFT) for Byzantine Fault Tolerant (BFT) state machine replication (SMR) under partial synchrony. SFT provides gradually increasing resilience guarantees during optimistic periods and allows committed blocks to tolerate up to two-thirds corruptions, an improvement over the typical one-third threshold. The solution maintains linear message complexity, unlike previous quadratic solutions, and shows efficiency in real-world scenarios.
Byzantine fault tolerant (BFT) state machine replication (SMR) is an important building block for constructing permissioned blockchain systems. In contrast to Nakamoto Consensus where any block obtains higher assurance as buried deeper in the blockchain, in BFT SMR, any committed block is secure has a fixed resilience threshold. In this paper, we investigate strengthened fault tolerance (SFT) in BFT SMR under partial synchrony, which provides gradually increased resilience guarantees (like Nakamoto Consensus) during an optimistic period when the network is synchronous and the number of Byzantine faults is small. Moreover, the committed blocks can tolerate more than one-third (up to two-thirds) corruptions even after the optimistic period. Compared to the prior best solution Flexible BFT which requires quadratic message complexity, our solution maintains the linear message complexity of state-of-the-art BFT SMR protocols and requires only marginal bookkeeping overhead. We implement our solution over the open-source Diem project, and give experimental results that demonstrate its efficiency under real-world scenarios.