Availability Model for Byzantine Fault-Tolerant Systems

The growth in the complexity and extensibility of computer systems have caused vulnerabilities such as exploitable software bugs and configuration flaws. In turn, confirming computer security is becoming an increasingly important task. Byzantine fault-tolerant algorithms are popularly used to allow systems automatically continue operating. In addition, Byzantine Fault-Tolerant Systems are used in blockchain networks, commonly in tandem with other consensus mechanisms. This study proposes an analytical availability model which is critical for the evaluation of fault-tolerant multi-server systems. A model is proposed based on continuous-time Markov chains to analyse the availability of Byzantine Fault-Tolerant systems. Numerical results are presented reporting availability as a function of the number of participants and the relative number of honest actors in the system. It can be concluded from the model that there is a non-linear relationship between the number of servers and availability inversely proportional to the number of nodes in the system. This relationship is further strengthened as the ratio of honest malicious nodes to the total number of nodes increases.