Crypto glossary
Nakamoto consensus
Nakamoto consensus is how Bitcoin agrees on one history: proof of work to propose blocks, the heaviest-chain rule for forks and probabilistic finality.
Named after Bitcoin's pseudonymous creator, Nakamoto consensus combines three ideas. Proof of work makes producing a block costly and selects proposers by lottery in proportion to hashrate. The heaviest-chain rule tells every node which branch to follow. And finality is probabilistic: each new block on top of a transaction makes reversing it exponentially more expensive.
Its breakthrough was letting an open, unknown and changing set of participants agree without registering identities, solving the Sybil problem that had blocked earlier digital cash designs. Litecoin, Dogecoin, Monero and many other proof-of-work coins use the same model, and several proof-of-stake designs borrow its longest-chain logic.
The price is slow and never absolute finality, high energy use and limited throughput. Classical Byzantine fault-tolerant protocols finalise blocks within seconds but need a known validator set; much of modern consensus research tries to combine the openness of Nakamoto consensus with faster, explicit finality.
Example
A merchant accepting a large bitcoin payment waits for six blocks, roughly an hour, because under Nakamoto consensus the chance of the payment being reversed shrinks with every block added.