> I read Antoine's original post on this and got the general gist, and > here also, it makes sense, but I'd like to ask: is it necessary that > (B, C) in the above not *see* A's opt-out "pre-replacement" (inputs: > A1, outputs: A, fees: low; call it TX_2)? I get that they cannot > replace it Is it actually true that they cannot replace it? If miners and node operators collude and have the incentive to run a patched version of core, is it still technically impossible to replace? > the idea that they suffer financial loss from > "ignorant" fee bumping is the part that seems weird to me. Even if they waste resources trying to fee-bump, I agree that this does not appear to be a catastrophe.There doesn't seem to be any technical reason why improvements can't be made to allow B and C to have a better view. Cheers, -Yancy On 2022-11-08 10:28, AdamISZ via bitcoin-dev wrote: > Hi aj and list, > (questions inline) > > ------- Original Message ------- > On Thursday, October 27th, 2022 at 18:21, Anthony Towns via > bitcoin-dev wrote: > >> Is that true? Antoine claims [1 [1]] that opt-in RBF isn't enough to >> avoid >> a DoS issue when utxos are jointly funded by untrusting partners, and, >> aiui, that's the main motivation for addressing this now. >> >> [1] >> https://lists.linuxfoundation.org/pipermail/lightning-dev/2021-May/003033.html >> >> The scenario he describes is: A, B, C create a tx: >> >> inputs: A1, B1, C1 [opts in to RBF] >> fees: normal >> outputs: >> [lightning channel, DLC, etc, who knows] >> >> they all analyse the tx, and agree it looks great; however just before >> publishing it, A spams the network with an alternative tx, double >> spending her input: >> >> inputs: A1 [does not opt in to RBF] >> fees: low >> outputs: A >> >> If A gets the timing right, that's bad for B and C because they've >> populated their mempool with the 1st transaction, while everyone else >> sees the 2nd one instead; and neither tx will replace the other. B and >> C can't know that they should just cancel their transaction, eg: >> >> inputs: B1, C1 [opts in to RBF] >> fees: 50% above normal >> outputs: >> [smaller channel, refund, whatever] >> >> and might instead waste time trying to fee bump the tx to get it >> mined, >> or similar. >> >> What should folks wanting to do coinjoins/dualfunding/dlcs/etc do to >> solve that problem if they have only opt-in RBF available? > > I read Antoine's original post on this and got the general gist, and > here also, it makes sense, but I'd like to ask: is it necessary that > (B, C) in the above not *see* A's opt-out "pre-replacement" (inputs: > A1, outputs: A, fees: low; call it TX_2)? I get that they cannot > replace it, but the idea that they suffer financial loss from > "ignorant" fee bumping is the part that seems weird to me. Clearly > TX_2 gets gossiped to other mempools; and understood that it does not > replace the TX_1 (the 3-input) in B's mempool, say, but why should > they not even hear about it? Is it just a matter of engineering, or is > there some deeper problem with that. > > About this general flavour of attack, it's never been a *big* concern > in Joinmarket imo (though, we did until recently have a bug that made > this happen *by accident*, i.e. people double spending an input out of > a negotiated join, albeit it was rare; but it's ofc definitely > *possible* to 'grief' like this, given the ordering of events; maker > sends signature, maker broadcasts double spend - 95% of the time they > will be first). Interactive protocols are yucky and I think there'll > always be griefing possibilities; designing around multiple-rounds of > negotiation amongst not always-on participants is even more yucky, so > just having a 'taker is in charge of network fee; if it's slow or gets > double spent out causing time delay then just wait', combined with > 'there really isn't any economic incentive for an attacker' (i.e. > ignoring griefing) might sound crappy but it's probably just being > realistic. > > Of course, off-chain contracting has more sophisticated considerations > than this. > > Cheers, > AdamISZ/waxwing > > _______________________________________________ > bitcoin-dev mailing list > bitcoin-dev@lists.linuxfoundation.org > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev Links: ------ [1] https://lists.linuxfoundation.org/pipermail/lightning-dev/2021-May/003033.html