[Lightning-dev] Penalty tx and RBF

Cezary Dziemian cezary.dziemian at gmail.com
Fri Nov 23 19:34:38 UTC 2018

Thanks for answer,

My knowledge is mostly based on this article:


Graph at the end shows that in order to claim former channel partner funds
I need to provide child transaction that contains my signature and secret.
This secret is evidence.that partner didn't commit the last transaction.

So the penalty transaction uses comitment transaction output as its input
and penalty transaction can be sign by one side only. Am I right, or I just
don't understand how it works? Or maybe this graph do not represents
correctly how commitment and penalty transactions are already developed?

Best Regards,
Cezary Dziemian

pt., 23 lis 2018 o 19:07 René Pickhardt <r.pickhardt at googlemail.com>

> Dear Cezary,
> as far as I understand the problem in the case of a unilateral (force)
> close are:
> 1.) In order to RBF your commitment transaction you would have to have the
> signature of your former channel partner. since you initiated a force close
> it is unlikely that you get this signature to RBF because then you could
> have done a mutual close right away which is cheaper since less tx are
> invovled to claim all funds back.
> 2.) In order to CPFP you have to be able to spend your output which can't
> work because there is a timelock on it.
> I believe on the last lightning developer summit this issue was discussed
> and it was agreed that for BOLT1.1 we want have a third output in the
> commitment transactions which anyone can spend (OP_TRUE) and which is just
> above the dust level. This output is supposed to have no timelock so that
> anyone can CPFP it. In the general case miners of the block could collect
> the output as a fee. You can find a pointer to this on this wikipage in the
> lightning-rfc git repo:
> https://github.com/lightningnetwork/lightning-rfc/wiki/Lightning-Specification-1.1-Proposal-States
> (look in the section tx and fees)
> best Rene
> On Fri, Nov 23, 2018 at 6:30 PM Cezary Dziemian <cezary.dziemian at gmail.com>
> wrote:
>> Hello all,
>> Sorry for my ignorance. I have two questions related with penalty txs. I
>> assume, that when someone commits obsolete commitment tx, my node
>> automatically commit penalty transaction.
>> What if fees suddenly increases? Can my node use RBF to increase fee?
>> Is there any approach common to major 3 implementations?
>> How much time (how many blocks) do my node have to commit penalty tx? Is
>> there some value common for implementations?
>> Best regards,
>> Cezary Dziemian
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> --
> https://www.rene-pickhardt.de
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