Rust-Lightning

Rust-Lightning is a Bitcoin Lightning library written in Rust. The main crate, lightning, does not handle networking, persistence, or any other I/O. Thus, it is runtime-agnostic, but users must implement basic networking logic, chain interactions, and disk storage. More information is available in the About section.

The lightning-net-tokio crate implements Lightning networking using the Tokio async runtime.

The lightning-persister crate implements persistence for channel data that is crucial to avoiding loss of channel funds. Sample modules for persistence of other Rust-Lightning data is coming soon.

Status

The project implements all of the BOLT specifications in the 1.0 spec. The implementation has pretty good test coverage that is expected to continue to improve. It is also anticipated that as developers begin using the API, the lessons from that will result in changes to the API, so any developer using this API at this stage should be prepared to embrace that. The current state is sufficient for a developer or project to experiment with it. Recent increased contribution rate to the project is expected to lead to a high quality, stable, production-worthy implementation in 2021.

Communications for Rust-Lightning and Lightning Development Kit happens through our LDK slack & discord channels.

Crates

1. lightning
   The Core of the LDK library, implements the lightning protocol, channel state machine, and on-chain logic. Supports no-std and exposes on relatively low-level interfaces.
2. lightning-background-processor Utilities to perform required background tasks for Rust Lightning.
3. lightning-block-sync Utilities to fetch the chain data from a block source and feed them into Rust Lightning.
4. lightning-invoice Data structures to parse and serialize BOLT11 lightning invoices.
5. lightning-net-tokio Implementation of the rust-lightning network stack using Tokio. For Rust-Lightning clients which wish to make direct connections to Lightning P2P nodes, this is a simple alternative to implementing the required network stack, especially for those already using Tokio.
6. lightning-persister Utilities to manage Rust-Lightning channel data persistence and retrieval.
7. lightning-rapid-gossip-sync Client for rapid gossip graph syncing, aimed primarily at mobile clients.

About

LDK/Rust-Lightning is a generic library which allows you to build a lightning node without needing to worry about getting all of the lightning state machine, routing, and on-chain punishment code (and other chain interactions) exactly correct. Note that Rust-Lightning isn't, in itself, a node. There are various working/in progress demos which could be used as a node today, but if you "just" want a generic lightning node, you're almost certainly better off with c-lightning/lnd - if, on the other hand, you want to integrate lightning with custom features such as your own chain sync, your own key management, your own data storage/backup logic, etc., LDK is likely your only option. Some Rust-Lightning utilities such as those in chan_utils are also suitable for use in non-LN Bitcoin applications such as DLCs and bulletin boards.

We are currently working on a demo node which fetches blockchain data and on-chain funds via Bitcoin Core RPC/REST. The individual pieces of that demo are/will be composable, so you can pick the off-the-shelf parts you want and replace the rest.

In general, Rust-Lightning does not provide (but LDK has implementations of):

• on-disk storage - you can store the channel state any way you want - whether Google Drive/iCloud, a local disk, any key-value store/database/a remote server, or any combination of them - we provide a clean API that provides objects which can be serialized into simple binary blobs, and stored in any way you wish.
• blockchain data - we provide a simple block_connected/block_disconnected API which you provide block headers and transaction information to. We also provide an API for getting information about transactions we wish to be informed of, which is compatible with Electrum server requests/neutrino filtering/etc.
• UTXO management - RL/LDK owns on-chain funds as long as they are claimable as a part of a lightning output which can be contested - once a channel is closed and all on-chain outputs are spendable only by the user, we provide users notifications that a UTXO is "theirs" again and it is up to them to spend it as they wish. Additionally, channel funding is accomplished with a generic API which notifies users of the output which needs to appear on-chain, which they can then create a transaction for. Once a transaction is created, we handle the rest. This is a large part of our API's goals - making it easier to integrate lightning into existing on-chain wallets which have their own on-chain logic - without needing to move funds in and out of a separate lightning wallet with on-chain transactions and a separate private key system.
• networking - to enable a user to run a full lightning node on an embedded machine, we don't specify exactly how to connect to another node at all! We provide a default implementation which uses TCP sockets, but, e.g., if you wanted to run your full lightning node on a hardware wallet, you could, by piping the lightning network messages over USB/serial and then sending them in a TCP socket from another machine.
• private keys - again we have "default implementations", but users can chose to provide private keys to RL/LDK in any way they wish following a simple API. We even support a generic API for signing transactions, allowing users to run RL/LDK without any private keys in memory/putting private keys only on hardware wallets.

LDK's customizability was presented about at Advancing Bitcoin in February 2020: https://vimeo.com/showcase/8372504/video/412818125

Design Goal

The goal is to provide a full-featured but also incredibly flexible lightning implementation, allowing the user to decide how they wish to use it. With that in mind, everything should be exposed via simple, composable APIs. More information about Rust-Lightning's flexibility is provided in the About section above.

For security reasons, do not add new dependencies. Really do not add new non-optional/non-test/non-library dependencies. Really really do not add dependencies with dependencies. Do convince Andrew to cut down dependency usage in rust-bitcoin.

Rust-Lightning vs. LDK (Lightning Development Kit)

Rust-Lightning refers to the core lightning crate within this repo, whereas LDK encompasses Rust-Lightning and all of its sample modules and crates (e.g. the lightning-persister crate), language bindings, sample node implementation(s), and other tools built around using Rust-Lightning for lightning integration or building a lightning node.

Tagline

"Rust-Lightning, not Rusty's Lightning!"

Contributing

Contributors are warmly welcome, see CONTRIBUTING.md.

Project Architecture

For a Rust-Lightning high-level API introduction, see ARCH.md.

License is either Apache-2.0 or MIT, at the option of the user (ie dual-license Apache-2.0 and MIT).