Subject: Re: [bitcoin-dev] [Lightning-dev] [Pre-BIP] Fee Accounts

From: Jeremy Rubin <[email-masked]>
Date: Sun, 20 Feb 2022 08:45:35 -0800

Morning!

>
> For the latter case, CPFP would work and already exists.
> **Unless** you are doing something complicated and offchain-y and involves
> relative locktimes, of course.
>
>
The "usual" design I recommend for Vaults contains something that is like:

{<maturity> CSV <pk_hot> CHECKSIG, <pk_cold> CHECKSIG}
or
{<maturity> CSV <pk_hot> CHECKSIG, <H(tx to: <pk_cold> CHECKSIG)> CTV}

where after an output is created, it has to hit maturity before hot
spendable but can be kicked to recovery any time before (optional: use CTV
to actually transition on chain removing hot wallet, if cold key is hard to
access).

Not that this means if you're waiting for one of these outputs to be
created on chain, you cannot spend from the hot key since it needs to
confirm on chain first. Spending from the cold key for CPFP'ing the hot is
an 'invalid move' (emergency key for non emergency sitch)

Thus in order to CPFP, you would need a separate output just for CPFPing
that is not subject to these restrictions, or some sort of RBF-able addable
input/output. Or, Sponsors.

Jeremy