The workshop was previously announced by ariard on the bitcoin-dev mailing list here: https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2021-April/018841.html
A reminder was posted to the bitcoin-dev mailing list here: https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2021-June/019068.html The conversation log for the workshop is here: https://gist.github.com/ariard/5f28dffe82ddad763b346a2344092ba4 I’ll summarize what was discussed during the meeting but please refer to the L2 zoology repo ariard has set up for background context and additional notes: https://github.com/ariard/L2-zoology General considerations I think it is worth first reiterating the obvious that there will never be perfect security guarantees on network transaction fee rates or transaction relay. Network fee rates can in theory go up to anything (upper limit of infinity) and will always to some degree be inherently unpredictable. In addition transaction acceptance can never be guaranteed even if you attempt a direct connection to a miner. At the same time L2 protocols (e.g. Lightning and DLCs) elevate transaction propagation and inclusion in a time sensitive mined block to a security assumption from what used to just be a usability assumption (BlueMatt). Within those confines these workshops are attempting to strengthen that security assumption knowing that guaranteeing it is out of reach. There are considerations that blocked transaction propagation isn’t necessarily a problem for the victim if it is also blocked for the attacker. In addition some successful attacks present an opportunity for the victim to divert their funds to miner fees (e.g. scorched earth) ensuring the attacker doesn’t financially benefit from the attack (harding). Personally I would argue neither of these present much assurance to the victim. Out of conservatism one should assume that the attacker has greater resources than the victim (e.g. a direct line to a miner) and knowing a victim’s lost funds went to the miner instead of the attacker isn’t of much comfort to the victim (other than potentially presenting a disincentive for the attack in the first place). This is obviously further complicated if the miner is the attacker. In addition any incentive for miners to not mine transactions to wait for a potential pay-all-to-fee are troubling (t-bast). New(ish) ideas RubenSomsen brought up the idea of fee sensitive timelocks, they would need a soft fork. ariard briefly discussed the idea of a transaction relay overlay network. harding stated his opinion that we should be leaning more on miners’ profit incentive rather than attempting to normalize mempool policy (e.g. https://lists.linuxfoundation.org/pipermail/lightning-dev/2020-April/002664.html). t-bast raised the prospect of mining pools exposing public APIs to push them transactions directly. The impact of changes to Bitcoin Core on L2 protocols Some changes to Core (e.g. some privacy improvements) can conflict with the goal of minimizing transaction propagation times. Chris_Stewart_5 raised the idea of a nightly bitcoind build to give L2 developers a way to write regression tests against the latest builds of bitcoind. He added that L2 devs should write automated regression test suites against bitcoind exposed RPC commands. t-bast would like a bitcoind “evicttx” RPC to remove a transaction from the mempool on regtest. Full RBF In advance of the workshop ariard posted to the mailing list a proposal for full RBF in a future version of Bitcoin Core: https://lists.linuxfoundation.org/pipermail/bitcoin-dev/2021-June/019074.html Progress in this direction has been attempted in the past (e.g. https://github.com/bitcoin/bitcoin/pull/10823) BlueMatt pointed out that even with full RBF it is trivial to create mempool partitions. As long as RBF has a fee rate increase minimum an attacker can trivially split the mempool by broadcasting two conflicting transactions with the same fee. ariard plans to contact businesses (e.g. Lightning onboarding services relying on zero confirmations) to check that this possible eventual move to full RBF doesn’t present a problem for them. There could well be engineering work required in advance of the possible change being made. Next week’s meeting Next week’s meeting (Tuesday 22nd June, 19:00 UTC, #l2-onchain-support, Libera) will be on fee bumping and package relay that glozow has recently been working to advance in Bitcoin Core. -- Michael Folkson Email: michaelfolk...@gmail.com Keybase: michaelfolkson PGP: 43ED C999 9F85 1D40 EAF4 9835 92D6 0159 214C FEE3 _______________________________________________ bitcoin-dev mailing list bitcoin-dev@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/bitcoin-dev
