Byzantine Fault Tolerance

Byzantine fault tolerance, or BFT, is a system's ability to keep operating correctly even when some participants fail arbitrarily — crashing, going silent, sending contradictory messages or actively lying. The name comes from the Byzantine generals problem, a thought experiment about commanders who must agree on a plan while some among them are traitors. Public blockchains face exactly this situation, because anyone can join and no participant can be trusted by default. Most BFT designs tolerate faulty participants up to roughly one third of the network; past that threshold, agreement can no longer be guaranteed. Proof of work, proof of stake and classical BFT protocols are simply different answers to the same underlying problem.