Byzantine Fault Tolerance (BFT)

What is Byzantine Fault Tolerance (BFT)?

In computer systems, a Byzantine fault refers to a scenario where a component experiences some sort of malfunction, but the data about the problem is inconsistent and unreliable. This can lead to a catastrophic failure if all actors involved in the system do not agree on a cohesive strategy to address the issue. BFT is the ability of a computer system to withstand and prevent these types of faults.

The term “Byzantine” comes from the historical problem of the Byzantine Generals, who had to coordinate their armies while facing unreliable communication and potential traitorous actors.
How BFT works

To achieve BFT, a system must establish rules that can effectively address Byzantine faults. This can be a complex process, as faults can occur anytime and require sophisticated code. To meet BFT criteria, a system must:
  • Start from an undetermined state without assuming the answer is “yes” or “no”
  • Use a reliable means of communication to share data and messages
  • Have nodes compute and reach a decided state
  • Use a voting process where the node with the most votes wins the state

BFT in blockchain technology

Many consensus protocols used in blockchain, such as Proof-of-Work (PoW), are also tolerant of Byzantine faults. These protocols allow a consensus to be reached in a Byzantine system under Byzantine conditions. For example, when developing the first cryptocurrency, Bitcoin, Satoshi Nakamoto implemented BFT using the PoW consensus protocol to ensure safe transactions.

Advantages and Disadvantages of BFT

Advantages include:
  • Guaranteed legitimacy of data in distributed systems, even in hostile scenarios
  • Ability to function in systems with unreliable or malicious actors
  • Increased security and reliability of transactions

Disadvantages include:
  • Complexity of implementation and maintenance
  • Increased energy consumption and resource requirements

BFT is a crucial aspect of blockchain technology and other decentralized systems. It ensures that data and transactions remain secure and legitimate, even in the presence of unreliable actors. As the use of blockchain technology continues to grow, BFT will become increasingly important to guarantee the integrity and reliability of digital systems.