Projects
project ideas for Qala development course
General
We are going to be building our own projects and contributing code to existing open source projects over the duration of the course.
Projects can be built as a front-end application, back end application, API or a command line tool.
You can use the suggested project list as inspiration for your third project. We want you to work on something that is useful to the community and can be maintained even after the Qala program.
Please run your own projects past the instructors first so we can check it is suitable and determine which skills it will require and exercise.
Your first project will involve making use of Lightning Network invoices and payments probably leverage a bitcoin or lightning library or development kit, in order to facilitate fast iteration on end results.
In your second/third project you should be considering not using a library to do as much of the heavy lifting, so that you can become more comfortable with how bitcoin and lightning work under the hood.
Mini design document
The first step for all the projects is to create a design document that describes your project / pull request and approach. The goal of this document is to:
think critically about what your application needs to do and what you'll need to achieve your goals
ensure the scope is neither too broad nor too narrow
enable early feedback to prevent spending too much time on an approach that may not be optimal
The design document should contain:
A basic outline of the project or PR.
Goals and non-goals. Define both what's in-, as well as out of scope.
For your application architecture (some of this may not be relevant to PRs):
Components: the building blocks of your application, and which technologies you'll use (e.g. Rust backend and Vue.js frontend)
Interface: which API endpoints, CLI commands or frontend views are required?
Code structure: high-level organization of folders, files, classes
Dependencies: (bitcoind/LND) RPC functions, libraries, ...
Introspection: what are the most difficult or risky parts of the project or PR, based on your own assessment of available skills?
What milestone you need to reach to consider the project have achieved Minimum Viable Product (MVP) state
Ensure to maximize your time being able to work on Bitcoin/LN related tasks. Non-critical general software engineering work should be removed from scope as much as possible.
Please create and share the design document using a collaborative document editor, so that we can add any comments or feedback that we have. Examples of editors https://hackmd.io and https://docs.google.com, but you can choose any you're familiar with so long as we can easily log in to comment.
Project 1 - "Magic internet money 🧙"
The purpose of this project is to demonstrate a basic working knowledge of Bitcoin and Lightning by building a way to accept Magic Internet Money! This project is meant to be simple, but don't worry: there will be plenty of time throughout the rest of the course for more complicated projects.
Goals
Demonstrate proficiency working on signet / testnet
Get experience with writing your first design document
Build a working payment workflow using either Bitcoin or Lightning
Address UX challenges users might face
Deliverables
A design document
Working infrastructure on signet / testnet
A simple application which requires someone to make a payment, either with Bitcoin or Lightning (or both!)
This can be built as a front-end application, back end application, API or a command line tool but it must be something a user can interact with
Confirmation to the user once payment has been received
This project is meant to be simple to allow you to get familiar with the process of writing a design doc and scoping features. Additionally, since you will all be working on the same prompt, you will be able to collaborate with your peers if you run into issues.
Timeline
Design document due by Friday, but the sooner the better
Project demo due the following Friday
Projects can still be a work in progress, the goal is to show what you've done so far
Project 2 - "Welcome to the community 🤗"
You're going to be doing some real contributing to existing open source projects in the wider community. We'll specifically be looking at project issues labelled as good first issue. You'll first have to attend the contributing etiquette workshop as it's very important we are respectful of maintainers' and other contributors' time and we know how to act appropriately.
Open Source Project List with Good First Issues
These are projects with which we are able to assist you.
Bitcoin Core - C++/Python
LDK - Rust
LND - Go
Liana Wallet - Rust
Rust Bitcoin - Rust
Buidl Library - Python
Rust Miniscript - Rust
BDK - Rust
Stratum V2 - Rust
BitcoinJS - TypeScript/JavaScript
Polar - TypeScript
Nigiri - Go/Docker
BlueWallet - JS/ReactNative
Galoy Repos - See tech stack
BTCPayServer - C#
Core Lightning - C/Python
Fedimint - Rust
Faraday - Go
If there is a project you want to contribute to that is not listed above, please let us know so that we can check them out and figure out if they're a good fit :)
TIP: Start small and don't try to understand the whole codebase. You'll encounter the codebase and architecture as you touch small and isolated issues. This will improve your experience and knowledge over time.
Prerequisites for starting on an issue
Please see the open source contribution notes.
Some mention on the issue that you are going to be working on it. This is also a good time to ask for tips/pointers on the issue.
Design doccuments are still necessary for this project. Be sure to at least include:
Why this issue is a good fit for you in terms of skills.
How you will go about implementing the fix/feature.
Project 3 - "Spread your wings 🦅"
It's come down to this, your final project. Here you're going to get your creativity flowing and work on something really great and beneficial to the wider Bitcoin community. If this project could be summarised in two words they would be "longevity" and "impact". We want you to do something meaningful here and make your big debut.
You can use any programming language with which you are familiar. Remember that this project is not meant for learning a new language, but to build an impactful Bitcoin/Lightning project - you have freedom to choose but don't let it be a barrier to accomplishing your primary goals!
Bitcoin projects
Topics to cover: transactions, scripting, reorgs, HD wallets
Tier 1
Tier 2
Satoshi dice
Outline: A provably fair gambling application, where payments to and from the casino are made on-chain or in Lightning. See bitcoin.it/wiki/Satoshi_Dice for more background information, and this Stack Exchange question for a high-level on-chain implementation.
Format: Casino server back-end (required); Client application (optional, GUI or CLI)
BTC/LN topics: creating and parsing Bitcoin transactions, 0-conf protocols, provable fairness
Fork monitor
Outline: Monitor blockchain and send an alert when a fork (exceeding n blocks) occurs, and another one when it is "resolved" (m blocks ahead)
Format: Server back-end; simple front-end or API to subscribe (email, pub/sub, webhooks, ...)
BTC/LN topics: chain reorgs, block propagation
Block explorer
Outline: given a block hash, visualize block header and transaction information. Given a transaction hash, visualize input and output information. See e.g. https://blockstream.info/
Format: Client application (GUI or CLI)
BTC/LN topics: parsing blocks, parsing transactions
Mempool fee analysis
Outline: Create a service which monitors the current state of the mempool with respect to fees. Provide APIs or a GUI which users (and optionally services) can connect to in order to retrieve relevant information. Include facility for users to upload their own transactions via the service.
Format: Backend with APIs or front end with GUI
BTC/LN topics: transactions, fees, mempool, p2p
P2P network analysis
Outline: Create a service which monitors messages over the P2P network. The service might be able to monitor node information such as user agent, version, services. Connection metrics such as uptime, churn could also be monitored. P2P traffic can also be inspected in order to determine message contents, e.g. transactions, blocks, as well as estimating bandwidth usage per message type. Provide APIs or a GUI which users (and optionally services) can connect to in order to retrieve relevant information.
Format: Backend with APIs or front end with GUI
BTC/LN topics: P2P, networking, mempool
Transaction propagation
Outline: Create a service which monitors messages over the P2P network from multiple endpoints in order to estimate transaction (and block) propagation times over the network. Consider that many bitcoin nodes may be running only connected to Tor or I2P networks.
Format: Backend with APIs or front end with GUI/graphs
BTC/LN topics: P2P, networking, mempool
Build your own signet
Outline: Create your own signet network with yourself as the primary "miner". In order to allow other miners to join in the future, use a signet challenge that related to a multisig address. Configure your signet to perform semi-regular re-orgs which can be used to test software in re-org situations. Have someone else connect to your signet either as a miner or a regular node, and start making transactions.
Format: Backend/CLI
BTC/LN topics: transactions, scripting, re-orgs
Bitcoin paywall
Outline: Implement a paywall which requires a micro-donation of bitcoin to remove. Whilst this style of paywall is largely not practicable on bitcoin mainnet today the implementation could be upgraded in a future project extension to use lightning.
Format: Library
BTC/LN topics: transactions
Bitkinship
Outline: Given two UTXOs, calculate how related they are
Format: Library and CLI
BTC/LN topics: transactions
Bonus: Given an xPub, calculate relatedness between all UTXOs belonging to xPub.
TABConf wallet overhaul
Outline: Overhaul the TABConf wallet. This might mean translating into a language you're familiar with and using a different bitcoin wallet library, or upgrading the UX.
Format: Casino server back-end (required); Client application (optional, GUI or CLI)
BTC/LN topics: creating and parsing Bitcoin transactions, 0-conf protocols, provable fairness
Bitcoin wallet contact lists
Outline: Improve bitcoin wallet "contact" lists by checking for bitcoin privacy best practices which could include coinselection based on the other contacts you’ve interacted with “coins known by…”, “coins known by other contacts” … etc.
When querying a contact, coin or transaction a (JSON?) response could be given which included warnings of address re-use etc. A pretty comprehensive overview of the commonly-used privacy heuristics can be found here.
Format:
Graph wallet UTXOs
Outline:
Format:
Exchange or remittance service
Outline:
Format:
Bitcoin bank
Outline: Bitcoin “bank” (hot, warm, cold wallet backend) A bitcoin bank provides security guarantees for its users by not storing all bitcoins online in a hot wallet. Instead a scheme should be devised whereby an attacker, even with total remote access to the bank's computers, cannot steal all the bitcoins. You may want to incorporate threshold multisignature schemes, timeouts, and other scripting capabilities. You should also decide how partially signed transactions can be communicated between different stages in the bank "vault", creating any required facilities to import/export, verify and sign for them. The bank will need some nominal amount of its total reserve in a hot wallet to perform everyday operations. Decide on an amount and also consider how hot and cold wallets will be balanced. Finally, consideration should be given to the privacy of your users and the privacy of your own bank when thinking about implementing any internal UTXO consolidation and transaction batching for user withdrawals.
Format: Software to manage the bank wallet. Optional frontend website for users to log in, see their balance and make deposits and withdrawals. If frontend website not provided, backend software should expose API to request transactions and user balances.
Chain analysis
Outline: Perform chain analysis on a set of provided UTXOs (or descriptors).
The collection of UTXOs that form a "wallet" can leak information with use over time. Providing information to users and wallets can help them (or their wallets) to make better decisions about which UTXOs to select in future transactions.
You can read more about "chainalysis" here: bitcoin privacy with OXT (and the following 3 parts of the blog). You can see some other implementations of wallet clustering/graphing here. A comprehensive overview of the commonly-used heuristics can be found here.
Decide on what information you want to reveal to the user. Decide which heuristics you'll need and how you will parse the blockchain.
Format: Can be an "all-in-one" (with frontend UI), backend only with endpoints, or as a library which other wallets could re-use.
Timelock refresher
Outline: To ensure your heirs can access your bitcoin after you pass away, all of your P2WSH addresses contain a second spending clause that after 1 year, a second key (held by your heir) can spend all of your outputs. With this program/script, you want to be able to quickly "refresh" all outputs that are coming close to being unlocked, e.g. within 3 months of the second spending path becoming viable. See https://bitcointalk.org/index.php?topic=5185907.0 for an example of the original setup.
Format: Client application, short lived.
BTC/LN topics: creating transaction, advanced scripting, timelocks
Bonus: multisig instead of single sig; use taproot
Multi-sig collaborative custody provider
Outline: Create your own service such as Casa that provides secure and collaborative custody of bitcoin. You need to create a 2-of-3 multi-sig wallet where the user holds two of the keys and the service holds one. In this setup, it's impossible for the service to move any user funds as they only posses a single key. In normal operation, the user makes use of both of their own keys and the service just coordinates the signing process. You must also allow the user to ask the service to sign with its key in the event the user does not have access to one of theirs. Allowing a hardware wallet as one of the user keys would be a bonus, where the client can interact with the hardware wallet to sign.
Format: Backend service and client (Web/Mobile)
JoinMarket UI
Outline: JoinMarket is an implementation of CoinJoin transactions that creates a market of makers who are available to take part in a CoinJoin at any time, and takers who can create a CoinJoin at any time. Your goal is to create a frontend UI for the JoinMarket client server that allows you to interact with JoinMarket in a more user-friendly manner. There is an effort such as JAM to do just this!
Format: Frontend UI (Web/Mobile)
Lightning projects
Satoshi dice/game
Satoshi's place
getAlby hacking
Messaging app
Something related to social networking
LND -> Core Lightning (CLN) database migration tool
Exchange / remittance service Look around Galoy for more ideas Ask Galoy
Build your own lightning node with LDK and accompanying crates (Rust)
A service involving submarine swaps
Where possible, try and use signet. It might be helpful to start off a project with regtest for easy iteration, but ideally it would be great to be able to interact with your projects from our end!
Lightning web store
Outline: Create a web store like starblocks.acinq.co that accepts signet lightning payments. You can sell any virtual products you want!
Format: Web front-end and a backend that communicates with LND
Network graph visualiser
Outline: Create a web application that shows a visualisation of the lightning network graph on signet. You will need a backend that communicates with LND (or another implementation if you wish) via a REST or equivalent API to get the channels and nodes in the graph. Your web application should update the graph in real time as nodes and channels are added or removed. You may use this tutorial as a starting point.
Format: Web front-end and a backend that communicates with LND.
Paywall
Outline: Create a simple paywalled website such as a blog or news site that requires you to pay some small fee in satoshis to be able to access content. One example is a site like yalls.org. It's important that the user does not need to pay more than once (for example, when refreshing their browser) so ensure that there is some way anonymously identify that a user has already paid by having some credential stored in a browser cookie. You can look into using something such as LSATs for this. There are libraries and proxies such as boltwall and aperture that can help.
Build your own lightning node
Outline: Build your own lightning node with the Lightning Development Kit (LDK) following the outline here. Use your bitcoind node (on signet) as a block source and wallet. Additionally, create a CLI tool that can interact with the node via RPCs, like lncli does for lnd. Your CLI should have commands to:
Generate an address to fund your on-chain wallet
Connect to a peer
List all peers
Open a channel with any other lightning node
List all channels
Create an invoice
Pay an invoice
Format: Lightning node with CLI
Submarine Swaps
Outline: Build a service that utilises Submarine Swaps between the bitcoin and lightning network. See the LND submarine swaps guide, the ION technical details, a nice guide from Muun wallet, the explanation from Alex Bosworth's Submarine Swap Service and this great explainer from Boltz, a decentralised swap service.
Also be sure to check out the Boltz Exchange itself.
Format: The service will essentially permit trustless swaps between the bitcoin and lightning network. It can be a website, CLI tool or other accessible service.
Bitcoin/LN libraries and tools you may find useful
The ecosystem of libraries for each language is quite diverse. Here are some of the most popular ones, but it's up to you to search for more. And remember, don't trust, verify!
Primary languages
The languages we highly encourage you to use for your first projects. All of you have indicated you know at least one of these and so it will make getting started and peer review much easier. We want to make sure that learning a new language does not get in the way of completing your first project in a timely manner. There will be ample opportunity to try out something like Go, Rust, and so on in future projects/exercises!
JavaScript/TypeScript
bitcoinjs-lib - A javascript Bitcoin library for node.js and browsers.
bolt11 - A library for encoding and decoding lightning network payment requests as defined in BOLT #11.
bip38 - BIP38 is a standard process to encrypt Bitcoin and crypto currency private keys that is less susceptible to brute force attacks thus protecting the user.
bip39 - JavaScript implementation of Bitcoin BIP39: Mnemonic code for generating deterministic keys
coinselect - An unspent transaction output (UTXO) selection module for bitcoin.
bitcoinjs Org - All the above and more!
boltwall - Bitcoin Lightning paywall and authentication using LSATs. Built with LND, Nodejs, and TypeScript.
bcrpc - Tiny Bitcoin RPC wrapper for Node.js.
bitcoinerlab/secp256k1 - A library for performing elliptic curve operations on the secp256k1 curve. It is designed to integrate into the BitcoinJS & BitcoinerLAB ecosystems and uses the audited noble-secp256k1 library.
bitcoinerlab/descriptors - A JavaScript library for parsing and interpreting Bitcoin descriptors, including those based on the Miniscript language.
Python
buidl - python3 bitcoin library with no dependencies and extensive test coverage
bitcoin-lib - "The Swiss Army Knife of the Bitcoin protocol." - Wladimir J. van der Laan
CLN plugins - Community curated plugins for core-lightning
python-mnemonic - Mnemonic code for generating deterministic keys, BIP39
python-bip380 - Bitcoin Output Script Descriptors with Miniscript extension - Work in progress, ready for hacking and contributions welcomed.
Other languages
We only encourage moving onto these languages after your first project, unless you have made an arrangement with one of the teachers.
Java
bitcoinj - A library for working with Bitcoin in Java.
Rust
bitcoin - Library with support for de/serialisation, parsing and executing on data-structures and network messages related to Bitcoin. You can use this library to create private keys and addresses, for PSBT operations and other nifty things.
bdk - Bitcoin Development Kit is a modern, lightweight, descriptor-based wallet library written in Rust! If you're looking for a great library with high-level APIs for building a Bitcoin wallet then check this out.
bitcoincore-rpc - Contains an implementation of an RPC client that exposes the Bitcoin Core JSON-RPC APIs as rust functions.
Some crates from LDK (check README):
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.
lightning-background-processor - Utilities to perform required background tasks for Rust Lightning.
lightning-block-sync - Utilities to fetch the chain data from a block source and feed them into Rust Lightning.
lightning-invoice Data - Structures to parse and serialise BOLT11 lightning invoices.
Go
Last updated