Modern Byzantine Fault-Tolerant State Machine Replication (BFT-SMR) solutions focus on reducing communication complexity, improving throughput, or lowering latency. This work explores the energy efficiency of BFT-SMR protocols. First, we propose a novel SMR protocol that optimizes for the steady state, i.e., when the leader is correct. This is done by reducing the number of required signatures per consensus unit and the communication complexity by order of the number of nodes n compared to the state-of-the-art BFT-SMR solutions. Concretely, we employ the idea that a quorum (collection) of signatures on a proposed value is avoidable during the failure-free runs. Second, we model and analyze the energy efficiency of protocols and argue why the steady-state needs to be optimized. Third, we present an application in the cyber-physical system (CPS) setting, where we consider a partially connected system by optionally leveraging wireless multicasts among neighbors. We analytically determine the parameter ranges for when our proposed protocol offers better energy efficiency than communicating with a baseline protocol utilizing an external trusted node. We present a hypergraph-based network model and generalize previous fault tolerance results to the model. Finally, we demonstrate our approach's practicality by analyzing our protocol's energy efficiency through experiments on a CPS test bed. In particular, we observe as high as 64% energy savings when compared to the state-of-the-art SMR solution for n=10 settings using BLE.

翻译：现代拜占庭容错状态机复制技术主要致力于降低通信复杂度、提升吞吐量或减少延迟。本文探索了拜占庭容错状态机复制协议的能效问题。首先，我们提出一种针对稳态（即领导者正确时）进行优化的新型状态机复制协议。该协议通过减少每个共识单元所需的签名数量，并将通信复杂度降至与节点数n同阶（相比当前最先进的拜占庭容错状态机复制方案），具体而言，我们利用了在无故障运行期间可避免对提议值进行法定签名（集合）的思想。其次，我们对协议的能效进行建模与分析，论证了为何需要对稳态进行优化。第三，我们给出一个信息物理系统场景下的应用实例，其中通过可选地利用邻居节点间的无线组播来考虑部分连接系统。我们通过分析确定了所提协议相对于使用外部可信节点的基线协议能提供更优能效的参数范围，并建立了基于超图的网络模型，将先前的容错结果推广至该模型。最后，通过在信息物理系统测试平台上进行能效实验，验证了所提方法的实用性。特别地，在n=10且使用BLE通信的设置下，相比当前最先进的状态机复制方案，我们观察到高达64%的能耗节省。