What is Byzantine Fault Tolerance (BFT)?

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Byzantine fault, is derived from the Problem of the Byzantine Generals (PGB). This logical problem infers that actors must agree on a good strategy to avoid fatal system failure. But there is a possibility that within the system there are actors that may not be reliable. As a result, the system must create mechanisms that guarantee that these malicious actors cannot destroy the system, beyond remedy. The creation of these mechanisms creates tolerance for Byzantine failures.

Any distributed ledger technology operates on the assumption that the network has some faults and should be able to remain functional even when the nodes fail to collaborate effectively due to non-malicious reasons. This could include when a node suddenly crashes or there is no response from a node, because he hasn’t received the message due to faults in communication protocol or the node being offline.

Byzantine Fault Tolerance is a measure that is set in place in blockchain technology to ensure that the network continues to operate even when a node or group of nodes fail or become malicious. It is the ability of a distributed ledger system to withstand Byzantine faults.

These failures can be:

  • Consensus failures.
  • Validation failures.
  • Data verification failures.
  • Failures in the response protocol against network situations.

However, there are different approaches for a blockchain to achieve Byzantine fault tolerance and this results in the development of different consensus algorithms.

How does this all relate to blockchain?

The most common consensus protocols used in blockchain networks such as proof-of-work, proof-of-stake, and proof-of-authority all have some property of BFT. By applying BFT, systems can be designed that are not controlled by a single authority and do not rely on trusting certain parties to keep the network running effectively. 

BFT  is essential to building a decentralized network. The principle of BFT will continue to play a major role in blockchain networks. As more people and organizations explore distributed and decentralized systems, more innovative ways to develop BFT systems will be discovered and implemented.