63 sats \ 4 replies \ @MiddleWay 22 Jun \ on: Free coinjoin coordination bitcoin
What happens if a fee is not enough? Who will CPFP the transaction (that will cost a lot)?
Also, I think for channel opening there won't be a privacy benefit, because gossip announcement channel size can be easily correlated with coinjoin input.
because gossip announcement channel size can be easily correlated with coinjoin input.
Public channels reveal to the world exactly which UTXO was associated with the channel; private channels do not. This is why mempool.space can label public LN channel opens with node IDs. For example: https://mempool.space/tx/37b07c1917fe814c4b504bd5a6746dd05d8140d6012d7d8b0e4321d91620db8d
LN does this as an anti-DoS measure. Without something similar to this you'd be able to advertise an infinite number of channels to the gossip network.
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Exactly that. Private channels already hide finding UTXO, and the public ones cannot even with coinjoin. Unless all inputs will be equal.
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What happens if a fee is not enough? Who will CPFP the transaction (that will cost a lot)?
Any participant can CPFP a stuck coinjoin, but it's disproportionately costly to attempt since they pay for the other participants. If you have a stuck coinjoin, you can double spend it by using a Libre relay node to duck under the BIP125 pools pinning your transaction: https://github.com/petertodd/bitcoin/tree/libre-relay-v27.1
Also, I think for channel opening there won't be a privacy benefit, because gossip announcement channel size can be easily correlated with coinjoin input.
The privacy benefit of coinjoining before onboarding to Lightning is that your channel UTXO can be known to anyone without them being able to see where you originally received funds on chain.
If you have a channel opened to you from an LSP, then you coinjoin after you close it so no one can link your previously used addresses or future on chain payments to your Lightning activity.
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Re: Libre Relay, people might be interested in my bitcoindev mailing list write-up on how it has been used by LN nodes to get pinned transactions unstuck: https://groups.google.com/g/bitcoindev/c/n2GNmnz0btw The Lightning protocol does have a few remaining transaction pinning vulnerabilities, so anyone running a LN node should consider running Libre Relay.
F2Pool has, so far, been the main pool fixing transaction pinning. I believe this is due to them having a shorter than usual transaction expiration time on their nodes; I don't think they're running replace-by-fee-rate itself.
A coinjoin with a fee that is too low is basically a case of accidental transaction pinning.
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