Another downside is that the sender may not opt into a non-pinnable future format like "V3 transactions", making CPFP difficult. They may spend a lot of fees to do this however, so maybe we're really reaching here.
On Wed, Oct 19, 2022 at 12:07 PM Sergej Kotliar via bitcoin-dev < bitcoin-dev@lists.linuxfoundation.org> wrote: > It's an interesting idea, presumably it would work w the new package relay. > Scorched earth bidding war is definitely fine to deter this type of abuse. > Need to consider it more thoroughly from all sides tho. CPFP on the server > side generally has a couple of downsides: > * Requires a hot wallet to receive bitcoin > * an entity that is reliably known to do CPFP can be abused by people > looking to consolidate utxos, which can be quite costly. Might be solvable > with a set of conditionals, and bad UX for abusers is less of a concern :) > > Will follow up after more deliberation, thanks! > > > On Wed, 19 Oct 2022 at 17:43, Jeremy Rubin <jeremy.l.ru...@gmail.com> > wrote: > >> If they do this to you, and the delta is substantial, can't you sweep all >> such abusers with a cpfp transaction replacing their package and giving you >> the original txn? >> >> On Wed, Oct 19, 2022, 7:33 AM Sergej Kotliar via bitcoin-dev < >> bitcoin-dev@lists.linuxfoundation.org> wrote: >> >>> Hi all, >>> >>> Chiming in on this thread as I feel like the real dangers of RBF as >>> default policy aren't sufficiently elaborated here. It's not only about the >>> zero-conf (I'll get to that) but there is an even bigger danger called the >>> american call option, which risks endangering the entirety of BIP21 "Scan >>> this QR code with your wallet to buy this product" model that I believe >>> we've all come to appreciate. Specifically, in a scenario with high >>> volatility and many transactions in the mempools (which is where RBF would >>> come in handy), a user can make a low-fee transaction and then wait for >>> hours, days or even longer, and see whether BTCUSD moves. If BTCUSD moves >>> up, user can cancel his transaction and make a new - cheaper one. The >>> biggest risk in accepting bitcoin payments is in fact not zeroconf risk >>> (it's actually quite easily managed), it's FX risk as the merchant must >>> commit to a certain BTCUSD rate ahead of time for a purchase. Over time >>> some transactions lose money to FX and others earn money - that evens out >>> in the end. But if there is an _easily accessible in the wallet_ feature to >>> "cancel transaction" that means it will eventually get systematically >>> abused. A risk of X% loss on many payments that's easy to systematically >>> abuse is more scary than a rare risk of losing 100% of one occasional >>> payment. It's already possible to execute this form of abuse with opt-in >>> RBF, which may lead to us at some point refusing those payments (even with >>> confirmation) or cumbersome UX to work around it, such as crediting the >>> bitcoin to a custodial account. >>> >>> To compare zeroconf risk with FX risk: I think we've had one incident in >>> 8 years of operation where a user successfully fooled our server to accept >>> a payment that in the end didn't confirm. To successfully fool (non-RBF) >>> zeroconf one needs to have access to mining infrastructure and probability >>> of success is the % of hash rate controlled. This is simply due to the fact >>> that the network currently won't propagage the replacement transaction to >>> the miner, which is what's being discussed here. American call option risk >>> would however be available to 100% of all users, needs nothing beyond the >>> wallet app, and has no cost to the user - only upside. >>> >>> Bitrefill currently processes 1500-2000 onchain payments every day. For >>> us, a world where bitcoin becomes de facto RBF by default, means that we >>> would likely turn off the BIP21 model for onchain payments, instruct >>> Bitcoin users to use Lightning or deposit onchain BTC to a custodial >>> account that we have. >>> This option is however not available for your typical >>> BTCPayServer/CoinGate/Bitpay/IBEX/OpenNode et al. Would be great to hear >>> from other merchants or payment providers how they see this new behavior >>> and how they would counteract it. >>> >>> Currently Lightning is somewhere around 15% of our total bitcoin >>> payments. This is very much not nothing, and all of us here want Lightning >>> to grow, but I think it warrants a serious discussion on whether we want >>> Lightning adoption to go to 100% by means of disabling on-chain commerce. >>> For me personally it would be an easier discussion to have when Lightning >>> is at 80%+ of all bitcoin transactions. Currently far too many bitcoin >>> users simply don't have access to Lightning, and of those that do and hold >>> their own keys Muun is the biggest wallet per our data, not least due to >>> their ease-of-use which is under threat per the OP. It's hard to assess how >>> many users would switch to Lightning in such a scenario, the communication >>> around it would be hard. My intuition says that the majority of the current >>> 85% of bitcoin users that pay onchain would just not use bitcoin anymore, >>> probably shift to an alt. The benefits of Lightning are many and obvious, >>> we don't need to limit onchain to make Lightning more appealing. As an >>> anecdote, we did experiment with defaulting to bech32 addresses some years >>> back. The result was that simply users of the wallets that weren't able to >>> pay to bech32 didn't complete the purchase, no support ticket or anything, >>> just "it didn't work 🤷♂️" and user moved on. We rolled it back, and later >>> implemented a wallet selector to allow modern wallets to pay to bech32 >>> while other wallets can pay to P2SH. This type of thing is clunky, and >>> requires a certain level of scale to be able to do, we certainly wouldn't >>> have had the manpower for that when we were starting out. This why I'm >>> cautious about introducing more such clunkiness vectors as they are >>> centralizing factors. >>> >>> I'm well aware of the reason for this policy being suggested and the >>> potential pinning attack vector for LN and other smart contracts, but I >>> think these two risks/costs need to be weighed against eachother first and >>> thoroughly discussed because the costs are non-trivial on both sides. >>> >>> Sidenote: On the efficacy of RBF to "unstuck" stuck transactions >>> After interacting with users during high-fee periods I've come to not >>> appreciate RBF as a solution to that issue. Most users (80% or so) simply >>> don't have access to that functionality, because their wallet doesn't >>> support it, or they use a custodial (exchange) wallet etc. Of those that >>> have the feature - only the power users understand how RBF works, and >>> explaining how to do RBF to a non-power-user is just too complex, for the >>> same reason why it's complex for wallets to make sensible non-power-user UI >>> around it. Current equilibrium is that mostly only power users have access >>> to RBF and they know how to handle it, so things are somewhat working. But >>> rolling this out to the broad market is something else and would likely >>> cause more confusion. >>> CPFP is somewhat more viable but also not perfect as it would require >>> lots of edge case code to handle abuse vectors: What if users abuse a >>> generous CPFP policy to unstuck past transactions or consolidate large >>> wallets. Best is for CPFP to be done on the wallet side, not the merchant >>> side, but there too are the same UX issues as with RBF. >>> In the end a risk-based approach to decide on which payments are >>> non-trivial to reverse is the easiest, taking account user experience and >>> such. Remember that in the fiat world card payments have up to 5% >>> chargebacks, whereas we in zero-conf bitcoin land we deal with "fewer than >>> 1 in a million" accepted transactions successfully reversed. These days we >>> have very few support issues related to bitcoin payments. The few that do >>> come in are due to accidental RBF users venting frustration about waiting >>> for their tx to confirm. >>> "In theory, theory and practice are the same. In practice, they are not" >>> >>> All the best, >>> Sergej Kotliar >>> CEO Bitrefill.com >>> >>> >>> -- >>> >>> Sergej Kotliar >>> >>> CEO >>> >>> >>> Twitter: @ziggamon <https://twitter.com/ziggamon> >>> >>> >>> www.bitrefill.com >>> >>> Twitter <https://www.twitter.com/bitrefill> | Blog >>> <https://www.bitrefill.com/blog/> | Angellist >>> <https://angel.co/bitrefill> >>> >>> >>> -- >>> >>> Sergej Kotliar >>> >>> CEO >>> >>> >>> Twitter: @ziggamon <https://twitter.com/ziggamon> >>> >>> >>> www.bitrefill.com >>> >>> Twitter <https://www.twitter.com/bitrefill> | Blog >>> <https://www.bitrefill.com/blog/> | Angellist >>> <https://angel.co/bitrefill> >>> _______________________________________________ >>> bitcoin-dev mailing list >>> bitcoin-dev@lists.linuxfoundation.org >>> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev >>> >> > > -- > > Sergej Kotliar > > CEO > > > Twitter: @ziggamon <https://twitter.com/ziggamon> > > > www.bitrefill.com > > Twitter <https://www.twitter.com/bitrefill> | Blog > <https://www.bitrefill.com/blog/> | Angellist <https://angel.co/bitrefill> > _______________________________________________ > bitcoin-dev mailing list > bitcoin-dev@lists.linuxfoundation.org > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev >
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