Crash Fault Tolerance vs Byzantine Fault Tolerance
Crash-fault protocols like Paxos and Raft tolerate f failures with 2f+1 replicas and majority quorums because a crashed node never lies; BFT needs 3f+1 replicas, 2f+1 quorums, an extra voting phase, and message authentication because faulty nodes can equivocate. CFT fits trusted data-center replication; BFT fits mutually distrusting parties such as blockchains.
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Crash-fault protocols like Paxos and Raft tolerate f failures with 2f+1 replicas and majority quorums because a crashed node never lies; BFT needs 3f+1 replicas, 2f+1 quorums, an extra voting phase, and message authentication because faulty nodes can equivocate. CFT fits trusted data-center replication; BFT fits mutually distrusting parties such as blockchains.
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