Submarine Swap provider plugin for CLN

This plugin is functional but experimental. Usage on mainnet is very reckless!

Please report any issues on GitHub and use only on testnet/signet.

There is one active instance of this plugin running on signet for client testing.

This Core Lightning plugin allows to the operator to act as provider for (reverse) submarine swaps to users of the Electrum Wallet (and others implementing the same, open protocol). Communication is facilitated via Nostr, and the plugin uses the CLN node's database, wallet and (newly derived) keys to operate, so the user does not have to manage any additional backup, wallet or Nostr identity.

Incentives (Reason to run this plugin alongside CLN)

The swap provider can charge a proportional fee for the liquidity provided. There is no risk of financial loss for the swap provider, as the swap is atomic and the mining fees required to unwind an unclaimed swap are settled by a separate lightning payment. A competitive fee can be chosen according to market conditions, fees of other providers can be seen in the Electrum Wallet.

Installation

Bitcoin Core backend

The Plugin relies on a Bitcoin Core backend Core Lightning is setup to use. Bitcoin Core has to enable txindex=1 for the plugin to work. The Plugin automatically uses the RPC credentials CLN is using and doesn't require any additional setup.

Plugin installation

You can find a detailed guide on how to install plugins in CLN using the reckless package manager -> here <-.

For reckless to find the plugin you first have to add this repository:

reckless source add https://github.com/f321x/nostr-subswap-provider-cln

Then you can install the plugin:

reckless install --network=signet swap-provider

Configuration

The plugin settings are configured using environment variables.

The following variables are available:

• NOSTR_RELAYS: A comma-separated string of nostr relay URIs. Example: wss://relay.damus.io,wss://relay.primal.net,wss://nos.lol
• SWAP_FEE_PPM: Fee to charge for swaps in ppm. Example: 10000 (1%)
• CONFIRMATION_TARGET_BLOCKS: Desired confirmation speed of onchain transactions. Example: 6
• FALLBACK_FEE_SATVB: Fallback feerate to use if no reliable fee estimation is possible. Example:65
• PLUGIN_LOG_LEVEL (optional): Level of Log output. Examples: DEBUG, INFO, WARNING, ERROR

Libraries

This plugin uses a lot of Electrum Wallet code that has been stripped/modified for this use case. It also uses the pyln-client library to communicate with CLN over the RPC interface.