Tendermint through the HotStuff lens: locks, unlocks, and evidence

A lock is memory, not “forever”

When a validator sees enough prevotes for a value it locks and must not vote for conflicting values without stronger evidence. An absolute lock would kill liveness, so Tendermint uses ValidRound and unlock rules that let the protocol progress without opening the door to two histories.

The same drama in another vocabulary

HotStuff keeps a lockedQC and proposes by extending highQC; Tendermint uses LockedValue, LockedRound, and ValidRound. Both negotiate between safety memory and the need for progress, and both must carry evidence when the round or view changes.

• prevote and precommit map to votes and certificates.
• ValidRound plays the role of the evidence that justifies a safe proposal.

Evidence and slashing are part of the protocol too

Proposer rotation lets the round advance when one proposer fails. If a validator signs two incompatible values, that evidence is propagated, stored for a valid window, and punished. The system does not merely assume honesty: it incentivizes it without creating new attack vectors.