Challenges May 2020

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Revision as of 09:50, 7 May 2020 by Renepickhardt (talk | contribs) (added proposal to look at JIT Routing, share balance information protocol)
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Projects with Challenges

This is the list of Lightning Network related projects that registered for this HackSprint so far (list grow soon):


Github issues with label "hackathon":

Video helping you to get started with RaspiBlitz development:

Chatroom to get started:


Chatroom to get started:

In a push to get lnbits new update out and extend its functionality, x3 0.03btc bounties are available for anyone developing extensions. If you're interested in making an extension, pop into the stream for a chat. If the community likes the idea, you can make it and on completion get one of the bounties!

see video:

Quickening - Room77 Point of Sale

Github issues starting with "Room77"

Chatroom to get started:


A service to give a Lightning node running behind TOR a port on a public IP address.

Subpage with Challenge: TOR2IP-Tunnelservice

Chatroom to get started:

Wiki Lightning Spam Protection

Turn this prototype to add a Lightning SpamProtection into a Media Wiki Extension thats easy to install and config on a standard Media Wiki.

Chatroom to get started:

SendMany App

Project Info:

Chatroom to get started:


Github issues with label "hackathon":

Chatroom to get started:

Bitcoin Bounty Hunt (Online FPS)

Challenges coming up.

Chatroom to get started:


This is the new name for the cheapnode project: Building the cheapest possible bitcoin fullnode (+lightning and other services) on old Android phones.

Help wanted on Github issues with label "hacksprint"

Chatroom to get started:

Rust Lightning network node

Another LN node? Why we need it?

The problem with the existing Lightning node implementations is their very limited extensibility for such things as:

  • future LN upgrades (channel factories, pay-to-ec-point, taproot),
  • protocols on top of LN (layer 3), like DLCs on LN or proposed Lightspeed payments, which require modification on the structure of the commitment transaction.

We will try to build a node that is highly modular and is ready for the future LN extensions. More information here:

During the hackathon we will try to:

  • compose core architecture with non-blocking multithreading
  • add lightning network wire protocol
  • implement BOLT-9 (using rust-lightning it should be simple)
  • implement BOLT-1: do connection to other LN nodes + send/receive `connect`, `ping` & `ping` messages
  • (optionally) implement gossip protocol

Contact User:Dr-Orlovsky for details

Chatroom to get started:

RTL (Ride The Lightning)

Github issues with label 'hackathon':

Chatroom to get started:


User:Cdecker is available on Mattermost for mentoring of c-lightning projects. Feel free to propose your own ideas, and we'll help you design and implement them :-)

Some ideas for projects / challenges:

  • Hardware wallet integration: c-lightning has supported external funding via the `fundchannel_start` and `fundchannel_complete` RPC methods for quite some time, in addition the `close_to` parameter allows you to specify where funds should be sent once the channel closes. These can be combined to have all on-chain funds sourced from a hardware wallet and, after they were borrowed to operate a channel, they can be returned to the hardware wallet. The idea here is to write a plugin that interacts with the hardware wallet to fund channels, so funds are only temporarily controlled by c-lightning.
  • `hsm_secret` generation from a seed-phrase: c-lightning will securely generate a random seed when first starting a new node. Given the lack of functional backup, and the seed not being sufficient to restore all the state, c-lightning has so not included any seed-phrase to restore the seed. However due to recent improvements both in backups and replicated DB backends, it would be great to also safely store the `hsm_secret` using existing tooling, such as paper backups, encrypted BIP39 seed-phrases, or even steel backups. Goal of this challenge is the creation of a launcher or plugin that takes a seed-phrase and generates the associated `hsm_secret` file.
  • Trampoline Proof-of-concept: Trampoline routing is a recent proposal to outsource some aspects of route-finding to another node in the neighborhood of the sending node. This is useful for nodes that may be unable to sync the network topology through gossip, or do not have time to sync before they need to send out a payment, e.g., mobile nodes. Using c-lightning's ability to implement custom protocol extensions (`custommsg`) and the ability to create routing onions with arbitrary payloads, you can implement a fast gossiping extension with which nodes announce their ability to route on behalf of others, and the sender to encapsulate the instructions for a trampoline node (where to go and how much to send).
  • Networked RPC interface: c-lightning is purposefully not exposing its JSON-RPC over the network, in order not to mandate a specific method of interaction. Plugins can take care of exposing the API in a variety of ways (grpc, JSON-RPC, REST, ...) and they can also be used to enforce arbitrary access policies using the `rpc_command` hook. These two aspects can be handled independently, i.e., one plugin exposes the API over some transport while another plugin enforces the authentication and authorization required to access the API. This in turn allows to mix and match arbitrary networked API endpoints and authentication mechanisms. Goal of this challenge is to come up with a generic way to have one plugin expose the API, and pass along any authentication information that was submitted with the request, so another plugin can enforce access policies.

JIT Routing / Sharing balance information

Recent - unpublished / work in progress - research that i am conducting suggests that JIT routing is indeed superior to our current path finding mechanism of probing channels until a path is found as JIT Routing

  • has on average a higher success rate
  • invokes on average less network communication messages to be sent
  • on average leaks less information of channel balances of the network to the sender / participating nodes
  • seems to prevent channel probing attacks (c.f: )

Previous research (c.f.: suggests that even without JIT rebalancing if the channel rebalancing is used proactively and opportunistically by nodes the overall payment success rates and routable amounts increase.

Thus on the Lightning Hacksprint we want to start working on a proof of concept implementation of JIT - routing. This effort has two parts:

  1. a communication protocol for nodes to share balance information with neighbors
  2. a modified transport layer for fee free rebalancing.

This weekend we will focus mainly on the communication protocol for sharing balance information with peers as an extension of BOLT7 as this would be needed in the JIT case and the proactive rebalancing case. If time permits we shall also look at the second goal to achieve fee free rebalancing.

We will write a spec for new gossip messages and provide a proof of concept as a c-lightning plugin. If time pemits we also invoke the rebalancing with fees during forwarding of HTLCs - which later can be exchanged with the fee free version.


To participate one should have a good understanding of BOLT1  which explains Lightning Messages and be familiar with BOLT07 which is about the gossip protocol which we plan to extend:

JIT Routing is explained at: The proposal for 2 (or more) new gossip messages to share balance information is initiated here: The Plugin API is documented here: most likely need

  • custommsg command

For invoking it at routing time we also need:

  • htcl_accepted Hook

It would be great to also come up with a fee free circular rebalancing protocol and transport but I guess this will not be achievable during the weekend.

Need more ideas?

Looking for yet another idea to build a small LApp? Check out Ideas for LApps!

Adding your Project

Feel free to add a challenge yourself! Ask Jeff or Rootzoll on the Mattermost for the password to edit the Wiki-Page. If you have a GitHub Repo best practice is to put the label "hackathon" (yellow) next to issues you like people to join/help for the weekend. If you added a challenge please also get in touch on Mattermost for more information and collaboration.