Low latency is one of the most desirable features of partially synchronous Byzantine consensus protocols. Existing low-latency protocols have achieved consensus with just two communication steps by reducing the maximum number of faults the protocol can tolerate (from $f = \frac{n-1}{3}$ to $f = \frac{n+1}{5}$), \textcolor{black}{by relaxing protocol safety guarantees}, or by using trusted hardware like Trusted Execution Environment. Furthermore, these two-step protocols don't support rotating primary and low-cost view change (leader replacement), which are important features of many blockchain use cases. In this paper, we propose a protocol called VBFT which achieves consensus in just two communication steps without scarifying desirable features. In particular, VBFT tolerates $f = \frac{n-1}{3}$ faults (which is the best possible), guarantees strong safety for honest primaries, and requires no trusted hardware. Moreover, VBFT supports primary rotation and low-cost view change, thereby improving prior art on multiple axes.

翻译：低延迟是部分同步拜占庭共识协议最受欢迎的特性之一。现有低延迟协议通过降低协议可容忍的最大故障节点数（从 $f = \frac{n-1}{3}$ 降至 $f = \frac{n+1}{5}$）、放宽协议安全保证或使用可信执行环境等可信硬件，仅需两个通信步骤即可达成共识。然而，这些两步协议不支持主节点轮换和低成本视图变更（领导者替换），而这正是许多区块链应用场景的重要特性。本文提出名为VBFT的协议，该协议在不牺牲上述重要特性的前提下，仅需两个通信步骤即可达成共识。具体而言，VBFT可容忍 $f = \frac{n-1}{3}$ 个故障节点（达到理论最优值），为诚实的首节点提供强安全性保证，且无需依赖可信硬件。此外，VBFT支持主节点轮换和低成本视图变更，从而在多个维度上改进了现有方案。