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（BFT-SMR）方案主要聚焦于降低通信复杂度、提升吞吐量或减少延迟。本研究探索了BFT-SMR协议的能效问题。首先，我们提出一种新型SMR协议，针对稳态（即领导者正确的情况）进行优化。通过减少每个共识单元所需的签名数量，并将通信复杂度相较于现有最优BFT-SMR方案降低节点数n的量级，该协议实现优化。具体而言，我们采用了在无故障运行期间可避免对提议值形成签名法定数（集合）的思想。其次，我们对协议的能效进行建模分析，论证为何需要优化稳态性能。第三，我们呈现一个网络物理系统（CPS）场景中的应用：通过可选地利用邻居节点间的无线多播，考虑部分连接的系统。我们通过分析确定参数范围，证明当采用本协议时，其能效优于使用外部可信节点的基线通信协议。我们提出基于超图的网络模型，并将先前容错结果推广至该模型。最后，通过在CPS测试平台上进行能效实验，验证了本方法的实用性。特别地，在采用BLE且n=10的配置下，与现有最优SMR方案相比，我们观察到高达64%的节能效果。