It would be interesting to pursue such integration. Do you have any thoughts on what the application you would like to see? I can see 4 directions:
There is a lightning channel between two non-canister entities. The canister is not directly involved in the channel but is somehow involved in the background, related to arranging or overseeing the lightning payments.
A channel is set up between a user and a canister to facilitate small, incremental payments from the user to the canister.
A channel is set up between a canister and a centralized service to facilitate small, incremental payments from the canister to the service.
A channel is set up between two canisters.
Lightning channel are usually used between two parties that do not fully trust each other. In scenario 2, if the user trusts the canister, then the lightning channel is not really needed. Instead, the user could just sent the whole amount (that he would otherwise lock up in the channel) to the canister, use some of the amount, and in the end ask the canister for a refund (instead of closing the channel).
If the user does not trust the target canister then presumably the user still trusts the integrity of the ckBTC canister. In that case, the user can just pay the target canister in small, incremental amounts in ckBTC. That would be even faster for the target to pick up than to accept a lightning payment. So in conclusion scenario 2 does not really benefit from lightning.
The same is true for scenario 4. For scenario 3 are there any interesting services that accept lightning and that a canister could use? If so this would be interesting to explore further.
In the short term I think that scenario 1 may have some real applications. Lightning has two problems: it requires constant backups of newly generated channel state data or otherwise the lightning node could lose funds. And it requires watching channel (watch towers). For both things a canister can help. So the setup would be a traditional lightning node and a canister that supports it in the background which benefits from being tamperproof, always online and can’t get destroyed. So the canister can serve as a backup target for channel data and also as a watchtower. The latter means that the canister, via the Bitcoin integration, can watch for the channel getting closed by the counterparty and it can submit the penalty transaction if the counterparty attempts to close it with an old state.
I am not sure the technical architecture given that’s not my skill set. Will leave that to @manu
But I do feel fairly confident (at least in short term) that lightning would be more trusted and adopted than ckBTC given it is trusted among maxis, including some very large players like Block.
Today, I can see maxis being excited to buy lightning on a ICP Dex using something like USDC as it’s a superior alternative to a CEX. It’s harder for me to see their excitement if they have to buy ckBTC. There’ll need to be a whole adoption and learning curve.
We are all playing for the long term with a big vision for a totally different kind of blockchain (crypto cloud) but it also helps to have short term catalysts for adoption.
There are pros and cons, and if it’s going to take another year and soak up foundation time then maybe it’s not worth it.
I would be curious to know though the user experience of a native lightning integration would be fairly similar to the user experience of ckBTC?