Distributed Consensus — Paxos, Raft, PBFT, and Nakamoto Consensus

Distributed consensus is not a vote in which everyone reaches the same opinion at the same instant. It is a set of rules that prevents correct participants from making contradictory decisions despite delay and failure; protocols differ in who may participate, which faults they tolerate, what they assume about time, and when a decision becomes final. Bitcoin did not merely scale up classical consensus: it tied influence to verifiable computational work in order to operate with open membership and Sybil identities.