Channel closure (force close)
Also · Force close · Cooperative close · Penalty
Closing a Lightning channel writes its final balance back to Bitcoin. It can be cooperative, forced by 1 side, or punitive when someone publishes an old state.
A channel ends in 1 of 3 ways. In a cooperative close, both parties sign a final transaction that pays each its balance right away, with a normal fee. In a force close, 1 party publishes its latest commitment transaction alone, because the other is offline or uncooperative. Its own funds are then locked for a delay, typically a few hundred blocks, that gives the counterparty time to object.
That delay exists for the third case. If the published state is an old, revoked one, the counterparty can use the revocation secret during the delay to claim the entire channel balance. Cheating is therefore made unprofitable rather than impossible, which is why staying online, or using a watchtower, matters.
In French · Fermeture de canal (force close)
