<blockquote>
  <p>What happens if B received the revocation key and decided to close the channel unilaterally without broadcasting the transaction</p>
</blockquote>

<p>By definition, channels are only closed once a commitment transaction or the closing transaction is broadcast. So B cannot close the channel; he simply withholds data from A.</p>

<hr>

<p>Your scenario is not possible because A will only give B the revocation key once both B has given A his new commitment transaction. So if B refuses to give A the revocation key to his commitment transaction, then A can close the channel by broadcast the previous commitment transaction which has not yet been revoked.</p>

CC BY-SA 3.0
2018-03-22T05:09:28.353Z
Thanks! Wouldn't it be unfair for B if A gets the new commitment, so he can broadcast both the old commitment and the new commitment? (especially in the case when the old commitment favors A).
Helin Wang
CC BY-SA 3.0
2018-03-22T05:19:25.770Z
The protocol is actually a bit more nuanced. A first sends B B's new commitment. When B accepts it, he has to send both the revocation key and A's new commitment before A sends B his revocation key. So if B refuses to send A the revocation key, A can close the channel unilaterally using the previous commitment which has not yet been revoked. I revised my answer slightly.
Ava Chow
CC BY-SA 3.0
2018-03-22T05:20:37.717Z
I suggest that you read this section of the lightning rfs: https://github.com/lightningnetwork/lightning-rfc/blob/master/02-peer-protocol.md#normal-operation
Ava Chow
CC BY-SA 3.0
2018-03-22T05:00:48.727Z
2018-03-22T05:20:05.523Z
2018-03-22T05:20:05.523Z
Ava Chow
<p>If I understands correctly, A and B will exchange their revocation key once they are ready to move to the next state. What happens if B received the revocation key and decided to close the channel unilaterally <em>without</em> broadcasting the transaction. This way B can never get his funds, but A can never get his funds as well. Because A can not broadcast his transaction since B has his revocation key. Isn't it a huge risk for A?</p>

<transactions><bitcoin-core><multi-signature><lightning-network>
Lightning networks revocable commitments: unilaterally closing could cause funds lost forever?
Helin Wang
# Lightning networks revocable commitments: unilaterally closing could cause funds lost forever?

(Asked by: username_0 on 2018-03-22)

If I understands correctly, A and B will exchange their revocation key once they are ready to move to the next state. What happens if B received the revocation key and decided to close the channel unilaterally *without* broadcasting the transaction. This way B can never get his funds, but A can never get his funds as well. Because A can not broadcast his transaction since B has his revocation key. Isn't it a huge risk for A?

**Tags:** transactions, bitcoin-core, multi-signature, lightning-network


---

## 1 answers

### Answer by username_1 on 2018-03-22. Score: 2 | Accepted answer

> What happens if B received the revocation key and decided to close the channel unilaterally without broadcasting the transaction

By definition, channels are only closed once a commitment transaction or the closing transaction is broadcast. So B cannot close the channel; he simply withholds data from A.

---

Your scenario is not possible because A will only give B the revocation key once both B has given A his new commitment transaction. So if B refuses to give A the revocation key to his commitment transaction, then A can close the channel by broadcast the previous commitment transaction which has not yet been revoked.

> **Comments:**
> **username_0**: Thanks! Wouldn't it be unfair for B if A gets the new commitment, so he can broadcast both the old commitment and the new commitment? (especially in the case when the old commitment favors A).  
> **username_1**: The protocol is actually a bit more nuanced. A first sends B B's new commitment. When B accepts it, he has to send both the revocation key and A's new commitment before A sends B his revocation key. So if B refuses to send A the revocation key, A can close the channel unilaterally using the previous commitment which has not yet been revoked. I revised my answer slightly.  
> **username_1**: I suggest that you read this section of the lightning rfs: https://github.com/lightningnetwork/lightning-rfc/blob/master/02-peer-protocol.md#normal-operation  

---

