BFTeam: Byzantine Fault Tolerance in Time- and Energy-Constrained Applications Under Memory Bounds

Future generations of the Internet of Things to a significant degree will consist of battery-free devices that only have a scarce amount of resources and harvest all the energy they consume from their environment. Since such small systems have to perform critical tasks, the affected data and computations need to be protected by means of redundant distribution across several nodes. Byzantine fault-tolerant (BFT) replication protocols are theoretically capable of meeting the demanded requirements in terms of reliability and availability, but unfortunately they are not directly applicable in resource-constrained embedded systems. This drawback is a result of the fact that existing BFT protocols were designed with server-based infrastructures in mind, which especially becomes evident in two aspects: Firstly, existing protocol implementations have a comparably large memory footprint and therefore are not suitable for small computing nodes, even with the protocols' minimal configuration. Secondly, existing approaches assume correct replicas to have a mostly uninterrupted power supply, meaning that their progress guarantees usually cannot be provided in systems in which temporary power failures may happen at any time.

The goal of the BFTeam project is to solve these shortcomings through whole-system runtime support for the operation of BFT protocols on embedded nodes. The special nature of this project lies in the cooperation between two research domains that in the past have largely been pursued independently from each other: (1) the development of resource-efficient protocols for the robust replication of applications and (2) the static analysis of embedded real-time systems to ensure upper bounds on execution time, energy consumption, and the size of a system's memory footprint. The joint BFTeam approach is the first that enables the analysis of critical protocol steps and phases in order to, for example, only execute these steps or phases if enough energy is available to actually complete them.

To achieve these goals, BFTeam first focuses on providing replica-local progress guarantees that affect only individual nodes but already suffice to support asynchronous BFT protocols. In a next step, the approach is then extended to also include system-wide guarantees for the entire replica group, thereby enabling the additional implementation of energy-aware partially synchronous protocols. For the evaluation of both the protocols and analysis techniques, BFTeam develops a hardware platform that is tailored to the specific requirements of the project. With this analyzable platform, BFTeam is able to assess the effectiveness of its solutions based on real-world experiments.

BFTeam is funded for 2 years by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) – 554710377.