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

分布式账本技术（dlt），通常被称为区块链，可以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dlt工作量证明机制存在操作延迟高和能源成本高的问题。拜占庭容错（BFT）共识协议被证明是工作量证明的潜在节能替代方案。然而，目前的BFT协议也存在一些挑战，这些挑战仍然限制了它们在生产系统中的实际应用。本研究项目通过(1)提高BFT共识协议的可扩展性而不降低其弹性来解决这些挑战，(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，即使在攻击下，考虑到环境条件，以及(3)支持有效的设计过程，自动化可测试的BFT系统从规范到部署区块链基础设施。可伸缩性的主题旨在找到实用的解决方案，这些解决方案可以考虑重大中断或升级后的恢复以及运行时的重新配置等挑战。我们还希望设计一个弹性通信层，将合适的通信拓扑的选择与实际的BFT共识协议解耦，从而降低其复杂性。这应该通过使用受信任的硬件组件来支持。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，我们希望能够分析可扩展的、复杂的BFT协议的效率（例如，在吞吐量和操作延迟方面），在将它们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。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目标攻击。第三个目标是在实际系统中支持系统和有效的实现，构建成建设性的模块化方法，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；结合基于启发式算法的自动化测试过程，使BFT系统中复杂的错误行为搜索空间更易于管理；以及用于自动部署的工具，并附带大规模dlt的基准测试和压力测试。

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.