rich1.0Bastien TEINTURIER [ARCHIVE] (npub17f…ntr0s)https://yabu.me/npub17fjkngg0s0mfx4uhhz6n4puhflwvrhn2h5c78vdr5xda4mvqx89swntr0snjumphttps://yabu.me📅 Original date posted:2020-10-05 📝 Original message: Good morning list, It seems to me that the "funder pays all the commit tx fees" rule exists solely for simplicity (which was totally reasonable). I haven't been able to find much discussion about this decision on the mailing list nor in the spec commits. At first glance, it's true that at the beginning of the channel lifetime, the funder should be responsible for the fee (it's his decision to open a channel after all). But as time goes by and both peers earn value from this channel, this rule becomes questionable. We've discovered since then that there is some risk associated with having pending HTLCs (flood-and-loot type of attacks, pinning, channel jamming, etc). I think that *in some cases*, fundees should be paying a portion of the commit-tx on-chain fees, otherwise we may end up with a web-of-trust network where channels would only exist between peers that trust each other, which is quite limiting (I'm hoping we can do better). Routing nodes may be at risk when they *receive* HTLCs. All the attacks that steal funds come from the fact that a routing node has paid downstream but cannot claim the upstream HTLCs (correct me if that's incorrect). Thus I'd like nodes to pay for the on-chain fees of the HTLCs they offer while they're pending in the commit-tx, regardless of whether they're funder or fundee. The simplest way to do this would be to deduce the HTLC cost (172 * feerate) from the offerer's main output (instead of the funder's main output, while keeping the base commit tx weight paid by the funder). A more extreme proposal would be to tie the *total* commit-tx fee to the channel usage: * if there are no pending HTLCs, the funder pays all the fee * if there are pending HTLCs, each node pays a proportion of the fee proportional to the number of HTLCs they offered. If Alice offered 1 HTLC and Bob offered 3 HTLCs, Bob pays 75% of the commit-tx fee and Alice pays 25%. When the HTLCs settle, the fee is redistributed. This model uses the on-chain fee as collateral for usage of the channel. If Alice wants to forward HTLCs through this channel (because she has something to gain - routing fees), she should be taking on some of the associated risk, not Bob. Bob will be taking the same risk downstream if he chooses to forward. I believe it also forces the fundee to care about on-chain feerates, which is a healthy incentive. It may create a feedback loop between on-chain feerates and routing fees, which I believe is also a good long-term thing (but it's hard to predict as there may be negative side-effects as well). What do you all think? Is this a terrible idea? Is it okay-ish, but not worth the additional complexity? Is it an amazing idea worth a lightning nobel? Please don't take any of my claims for granted and challenge them, there may be negative side-effects I'm completely missing, this is a fragile game of incentives... Side-note: don't forget to take into account that the fees for HTLC transactions (second-level txs) are always paid by the party that broadcasts them (which makes sense). I still think this is not enough and can even be abused by fundees in some setups. Thanks, Bastien -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.linuxfoundation.org/pipermail/lightning-dev/attachments/20201005/521584fe/attachment.html>