In this document, I compare two existing technologies for paying L1 bitcoin addresses from lightning channels, and then introduce a new protocol for this.
In bitcoin’s lightning network (LN), capital is typically allocated into structures called channels where two channel users split up the total balance of a utxo via presigned transactions. Additional off-chain transactions allow the two users to modify the balance they can withdraw from their channel as well as use a procedure called “routing” to chain transactions and channels together and thus pay other people without doing an L1 transaction.
Sometimes, a channel user wants to make an L1 transaction and pay a standard bitcoin address, but all their money is in an LN channel. There are two main solutions that allow this: splice-outs and swap-outs, which I will henceforth call splices and swaps.