Byzantine Fault Tolerance (BFT)
A system's ability to keep agreeing on the truth even when some participants fail or actively lie.
Byzantine fault tolerance is the property of reaching agreement despite some nodes being broken or malicious. The name comes from a thought experiment about generals who must coordinate while some send false messages.
For a blockchain, this is the hard problem: stay correct when you can't trust every participant. Consensus mechanisms exist to solve it. Most BFT designs hold up as long as dishonest actors stay below a threshold, often one-third of the network.
Related terms
The rules a decentralized network follows to agree on one valid history without trusting any central party.
FinalityThe point at which a confirmed transaction can no longer be reversed or pushed off the chain.
DecentralizationSpreading control and data across many independent participants so no single party can dictate or shut things down.
Sybil AttackAn attack where one actor spins up many fake identities to gain outsized influence over a network.