If the parties trust each other, rbf is still opt-in. Just don't do it? On Sat, Jun 26, 2021, 9:30 AM Billy Tetrud via bitcoin-dev < bitcoin-dev@lists.linuxfoundation.org> wrote: > > services providers are offering zero-conf channels, where you can start > to spend instantly [0]. I believe that's an interesting usage > > I agree those are interesting and useful cases. I suppose I should clarify > that when I asked if bitcoin should continue supporting 0-conf > transactions, I meant: should we make design decisions based on whether it > makes raw 0-conf transactions more or less difficult to double spend on? I > do think 0-conf transactions can be useful in situations where there is > some level of trust (either direct trust between the interacting parties, > or disperse trust that most people won't try to double spend, perhaps > because the transaction is small or their identity is tied to it). Fidelity > bonds sound like an interesting way to mitigate sybil attacks in a > reputation system. > > On Thu, Jun 24, 2021 at 5:23 PM Antoine Riard > wrote: > >> > Do we as a community want to support 0-conf payments in any way at this >> > point? It seems rather silly to make software design decisions to >> > accommodate 0-conf payments when there are better mechanisms for fast >> > payments (ie lightning). >> >> Well, we have zero-conf LN channels ? Actually, Lightning channel funding >> transactions should be buried under a few blocks, though few services >> providers are offering zero-conf channels, where you can start to spend >> instantly [0]. I believe that's an interesting usage, though IMHO as >> mentioned we can explore different security models to make 0-conf safe >> (reputation/fidelity-bond). >> >> > One question I have is: how does software generally inform the user >> about >> 0-conf payment detection? >> >> Yes generally it's something like an "Unconfirmed" annotation on incoming >> txn, though at least this is what Blockstream Green or Electrum are doing. >> >> > But I >> suppose it would depend on how often 0-conf is used in the bitcoin >> ecosystem at this point, which I don't have any data on. >> >> There are few Bitcoin services well-known to rely on 0-conf. Beyond how >> much of the Bitcoin traffic is tied to a 0-conf is a hard question, a lot >> of 0-confs service providers are going to be reluctant to share the >> information, for a really good reason you will learn a subset of their >> business volumes. >> >> I'll see if I can come up with some Fermi estimation on this front. >> >> [0] https://www.bitrefill.com/thor-turbo-channels/ >> >> Le mer. 16 juin 2021 à 20:58, Billy Tetrud a >> écrit : >> >>> Russel O'Connor recently opined >>> >>> that RBF should be standard treatment of all transactions, rather than as a >>> transaction opt-in/out. I agree with that. Any configuration in a >>> transaction that has not been committed into a block yet simply can't be >>> relied upon. Miners also have a clear incentive to ignore RBF rules and >>> mine anything that passes consensus. At best opting out of RBF is a weak >>> defense, and at worst it's simply a false sense of security that is likely >>> to actively lead to theft events. >>> >>> Do we as a community want to support 0-conf payments in any way at this >>> point? It seems rather silly to make software design decisions to >>> accommodate 0-conf payments when there are better mechanisms for fast >>> payments (ie lightning). >>> >>> One question I have is: how does software generally inform the user >>> about 0-conf payment detection? Does software generally tell the user >>> something along the lines of "This payment has not been finalized yet. All >>> recipients should wait until the transaction has at least 1 confirmation, >>> and most recipients should wait for 6 confirmations" ? I think unless we >>> pressure software to be very explicit about what counts as finality, users >>> will simply continue to do what they've always done. Rolling out this >>> policy change over the course of a year or two seems fine, no need to rush. >>> But I suppose it would depend on how often 0-conf is used in the bitcoin >>> ecosystem at this point, which I don't have any data on. >>> >>> On Tue, Jun 15, 2021 at 10:00 AM Antoine Riard via bitcoin-dev < >>> bitcoin-dev@lists.linuxfoundation.org> wrote: >>> >>>> Hi, >>>> >>>> I'm writing to propose deprecation of opt-in RBF in favor of full-RBF >>>> as the Bitcoin Core's default replacement policy in version 24.0. As a >>>> reminder, the next release is 22.0, aimed for August 1st, assuming >>>> agreement is reached, this policy change would enter into deployment phase >>>> a year from now. >>>> >>>> Even if this replacement policy has been deemed as highly controversial >>>> a few years ago, ongoing and anticipated changes in the Bitcoin ecosystem >>>> are motivating this proposal. >>>> >>>> # RBF opt-out as a DoS Vector against Multi-Party Funded Transactions >>>> >>>> As explained in "On Mempool Funny Games against Multi-Party Funded >>>> Transactions'', 2nd issue [0], an attacker can easily DoS a multi-party >>>> funded transactions by propagating an RBF opt-out double-spend of its >>>> contributed input before the honest transaction is broadcasted by the >>>> protocol orchester. DoSes are qualified in the sense of either an attacker >>>> wasting timevalue of victim's inputs or forcing exhaustion of the >>>> fee-bumping reserve. >>>> >>>> This affects a series of Bitcoin protocols such as Coinjoin, onchain >>>> DLCs and dual-funded LN channels. As those protocols are still in the early >>>> phase of deployment, it doesn't seem to have been executed in the wild for >>>> now. That said, considering that dual-funded are more efficient from a >>>> liquidity standpoint, we can expect them to be widely relied on, once >>>> Lightning enters in a more mature phase. At that point, it should become >>>> economically rational for liquidity service providers to launch those DoS >>>> attacks against their competitors to hijack user traffic. >>>> >>>> Beyond that, presence of those DoSes will complicate the design and >>>> deployment of multi-party Bitcoin protocols such as payment >>>> pools/multi-party channels. Note, Lightning Pool isn't affected as there is >>>> a preliminary stage where batch participants are locked-in their funds >>>> within an account witnessScript shared with the orchestrer. >>>> >>>> Of course, even assuming full-rbf, propagation of the multi-party >>>> funded transactions can still be interfered with by an attacker, simply >>>> broadcasting a double-spend with a feerate equivalent to the honest >>>> transaction. However, it tightens the attack scenario to a scorched earth >>>> approach, where the attacker has to commit equivalent fee-bumping reserve >>>> to maintain the pinning and might lose the "competing" fees to miners. >>>> >>>> # RBF opt-out as a Mempools Partitions Vector >>>> >>>> A longer-term issue is the risk of mempools malicious partitions, where >>>> an attacker exploits network topology or divergence in mempools policies to >>>> partition network mempools in different subsets. From then a wide range of >>>> attacks can be envisioned such as package pinning [1], artificial >>>> congestion to provoke LN channels closure or manipulation of >>>> fee-estimator's feerate (the Core's one wouldn't be affected as it relies >>>> on block confirmation, though other fee estimators designs deployed across >>>> the ecosystem are likely going to be affected). >>>> >>>> Traditionally, mempools partitions have been gauged as a spontaneous >>>> outcome of a distributed systems like Bitcoin p2p network and I'm not aware >>>> it has been studied in-depth for adversarial purposes. Though, deployment >>>> of second-layer >>>> protocols, heavily relying on sanity of a local mempool for >>>> fee-estimation and robust propagation of their time-sensitive transactions >>>> might lead to reconsider this position. Acknowledging this, RBF opt-out is >>>> a low-cost partitioning tool, of which the existence nullifies most of >>>> potential progresses to mitigate malicious partitioning. >>>> >>>> >>>> To resume, opt-in RBF doesn't suit well deployment of robust >>>> second-layers protocol, even if those issues are still early and deserve >>>> more research. At the same time, I believe a meaningful subset of the >>>> ecosystem are still relying >>>> on 0-confs transactions, even if their security is relying on far >>>> weaker assumptions (opt-in RBF rule is a policy rule, not a consensus one) >>>> [2] A rapid change of Core's mempool rules would be harming their quality >>>> of services and should be >>>> weighed carefully. On the other hand, it would be great to nudge them >>>> towards more secure handling of their 0-confs flows [3] >>>> >>>> Let's examine what could be deployed ecosystem-wise as enhancements to >>>> the 0-confs security model. >>>> >>>> # Proactive security models : Double-spend Monitoring/Receiver-side >>>> Fee-Topping with Package Relay >>>> >>>> From an attacker viewpoint, opt-in RBF isn't a big blocker to >>>> successful double-spends. Any motivated attacker can modify Core to >>>> mass-connect to a wide portion of the network, announce txA to this subset, >>>> announce txA' to the >>>> merchant. TxA' propagation will be encumbered by the privacy-preserving >>>> inventory timers (`OUTBOUND_INVENTORY_BROADCAST_INTERVAL`), of which an >>>> attacker has no care to respect. >>>> >>>> To detect a successful double-spend attempt, a Bitcoin service should >>>> run few full-nodes with well-spread connection graphs and unlinkable >>>> between them, to avoid being identified then maliciously partitioned from >>>> the rest of the network. >>>> >>>> I believe this tactic is already deployed by few Bitcoin services, and >>>> even one can throw flame at it because it over consumes network resources >>>> (bandwidth, connection slots, ...), it does procure a security advantage to >>>> the ones doing it. >>>> >>>> One further improvement on top of this protection could be to react >>>> after the double-spend detection by attaching a CPFP to the merchant >>>> transaction, with a higher package feerate than the double-spend. Expected >>>> deployment of package-relay as a p2p mechanism/mempool policy in Bitcoin >>>> Core should enable it to do so. >>>> >>>> # Reactive security models : EconomicReputation-based Compensations >>>> >>>> Another approach could be to react after the fact if a double-spend has >>>> been qualified. If the sender is already known to the service provider, the >>>> service account can be slashed. If the sender is a low-trusted >>>> counterparty to the merchant, "side-trust" models could be relied on. For >>>> e.g a LN pubkey with a stacked reputation from your autopilot, LSATs, stake >>>> certificates, a HTLC-as-a-fidelity-bond, ... The space is quite wide there >>>> but I foresee those trust-minimized, decentralized solutions being adopted >>>> by the LN ecosystem to patch the risks when you enter in a channel/HTLC >>>> operation with an anonymous counterparty. >>>> >>>> What other cool new tools could be considered to enhance 0-confs >>>> security ? >>>> >>>> To conclude, let's avoid replaying the contentious threads of a few >>>> years ago. What this new thread highlights is the fact that a transaction >>>> relay/mempool acceptance policy might be beneficial to some class of >>>> already-deployed >>>> Bitcoin applications while being detrimental to newer ones. How do we >>>> preserve the current interests of 0-confs users while enabling upcoming >>>> interests of fancy L2s to flourish is a good conversation to have. I think. >>>> >>>> If there is ecosystem agreement on switching to full-RBF, but 0.24 >>>> sounds too early, let's defer it to 0.25 or 0.26. I don't think Core has a >>>> consistent deprecation process w.r.t to policy rules heavily relied-on by >>>> Bitcoin users, if we do so let sets a precedent satisfying as many folks as >>>> we can. >>>> >>>> Cheers, >>>> Antoine >>>> >>>> [0] >>>> https://lists.linuxfoundation.org/pipermail/lightning-dev/2021-May/003033.html >>>> >>>> [1] See scenario 3 : >>>> https://lists.linuxfoundation.org/pipermail/lightning-dev/2020-June/002758.html >>>> >>>> [2] >>>> https://github.com/bitcoin/bitcoin/pull/10823#issuecomment-466485121 >>>> >>>> [3] And the LN ecosystem does have an interest to fix zero-confs >>>> security, if "turbo-channels"-like become normalized for mobile nodes >>>> _______________________________________________ >>>> bitcoin-dev mailing list >>>> bitcoin-dev@lists.linuxfoundation.org >>>> https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev >>>> >>> _______________________________________________ > bitcoin-dev mailing list > bitcoin-dev@lists.linuxfoundation.org > https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev >