[Lightning-dev] Both-side funded channels

ZmnSCPxj ZmnSCPxj at protonmail.com
Wed Sep 12 04:40:27 UTC 2018

Good morning Cezary,

> Thanks for answer,
> Do I understand what you described correctly? If some merchant would like to just start using ln by receiving funds, he need to:
> 1. Fund channel with amount he would like to be able to receive + dust_limit*2
> 2. Wait for confirmations to channel opening
> 3. Buy onchain bitcoins for ln bitcoins
> Weaknesses are:
> - he need to posses all funds he would like to receive + dust_limit*2

No.  Like I mentioned, the entire process can be repeated using "the same" onchain bitcoins.  The bitcoin you bought back may be used to open another channel with slightly smaller capacity (since fees will be deducted from it).  The process can be repeated, until your total capacity need is fulfilled or the swap service runs out of onchain funds.

Presumably you would require, say, a few dozen times the cost of the item you are selling for each channel.  You create a channel, reverse its direction (by buying onchain bitcoin), create a new channel again using the onchain bitcoin you bought back, and so on, getting several times of your initial funds as incoming capacity.  Depending on how much you open each time, the fees will be small compared to the channel size, and you can open one last channel (and *not* reverse it) to pay any employees, suppliers, and stockholders you have.

> - process takes longer
> - process requires 2 on-chain transactions
> - point 3 should be implemented in trustless way, so it also requires some development

Indeed, the number of onchain transactions is an issue.  Lightning could offer some kind of transactional cut-through, which would be a generalization of both splicing and dual-funding.

> Don't you agree with me, that right now there is no good way to initiate such receiving channel? Don't you think this is quite high weakness of LN?

No.  People who have kept their node consistently online for a few months generally find that they get incoming capacity anyway; you can simply trade off between time and money in this case.

> BTW Maybe there is someone who is working on this trustless swap between on-chain and on-channel funds?

As mentioned in another mail, submarine swaps. I have not looked into it in detail so cannot recommend yet, but others may know better.

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