BFT2Chain: Design and validation of scalable, Byzantine fault tolerant consensus algorithms for blockchains

分布式分类帐技术(DLTS)，通常被称为区块链，能够在没有中央基础设施的情况下实现可靠和抗攻击的服务。然而，广泛使用的用于DLT的工作证明机制存在操作延迟高和巨大的能源成本的问题。拜占庭容错(BFT)共识协议被证明是工作证明的一种潜在的节能替代方案。然而，当前的BFT协议也带来了挑战，仍然限制了它们在生产系统中的实际使用。本研究项目通过(1)在不降低BFT共识协议弹性的情况下提高BFT共识协议的可扩展性，(2)应用建模方法，使这些协议的预期性能和定时行为更可预测，甚至考虑到环境条件，以及(3)支持有效的、自动化的可测试BFT系统的设计过程，从规范到区块链基础设施中的部署，从而解决这些挑战。可伸缩性的主题旨在找到考虑到挑战的实用解决方案，例如从重大停机或升级中恢复以及在运行时重新配置。我们还希望设计一个弹性通信层，将选择合适的通信拓扑与实际的BFT共识协议解耦，从而降低其复杂性。这应该通过使用可信的硬件组件来支持。此外，我们希望研究这些概念与合适的加密原语的组合，以进一步提高可伸缩性。使用系统建模技术，我们希望能够在将可扩展、复杂的BFT协议部署到真实环境之前，基于系统大小、节点的计算能力和通信链路的基本特征的知识，分析它们的效率(例如，在操作的吞吐量和延迟方面)。我们还希望研究强大的对策，以帮助防御大规模区块链系统中的定向攻击。第三个目标是支持在实际系统中系统和有效地实施，结构成建设性的、模块化的方法，其中可验证的BFT协议是基于较小的、可验证的构建块组装的；纳入基于启发式算法的自动化测试程序，使BFT系统中行为不当的复杂搜索空间更易于管理；以及一个用于大规模DLT中的自动化部署以及伴随的基准和压力测试的工具。

Distributed Ledger Technologies (DLTs), often referred to as blockchains, enable the realisation of reliable and attack-resilient services without a central infrastructure. However, the widely used proof-of-work mechanisms for DLTs suffer from high latencies of operations and enormous energy costs. Byzantine fault-tolerant (BFT) consensus protocols prove to be a potentially energy-efficient alternative to proof-of-work. However, current BFT protocols also present challenges that still limit their practical use in production systems. This research project addresses these challenges by (1) improving the scalability of BFT consensus protocols without reducing their resilience, (2) applying modelling approaches for making the expected performance and timing behaviour of these protocols more predictable, even under attacks, taking into consideration environmental conditions, and (3) supporting the design process for valid, automated testable BFT systems from specification to deployment in a blockchain infrastructure. The topic of scalability aims at finding practical solutions that take into account challenges such as recovery from major outages or upgrades, as well as reconfigurations at runtime. We also want to design a resilient communication layer that decouples the choice of a suitable communication topology from the actual BFT consensus protocol and thus reduces its complexity.This should be supported by the use of trusted hardware components. In addition, we want to investigate combinations of these concepts with suitable cryptographic primitives to further improve scalability. Using systematic modelling techniques, we want to be able to analyse the efficiency of scalable, complex BFT protocols (for example, in terms of throughput and latency of operations), already before deploying them in a real environment, based on knowledge of system size, computational power of nodes, and basic characteristics of the communication links. We also want to investigate robust countermeasures that help defending against targeted attacks in large-scale blockchain systems. The third objective is to support the systematic and valid implementation in a practical system, structured into a constructive, modular approach, in which a validatable BFT protocol is assembled based on smaller, validatable building blocks; the incorporation of automated test procedures based on a heuristic algorithm which makes the complex search space of misbehaviour in BFT systems more manageable; and a tool for automated deployment with accompanying benchmarking and stress testing in large-scale DLTs.