Spiral Blockchain Engineer at Block in Paris, Île-de-France, France

Spiral (formerly Square Crypto) builds and funds free, open-source projects that advance the use of bitcoin as a tool for economic empowerment. The core team is mainly focused on contributing to the Lightning Development Kit (LDK), a tool that simplifies how developers add the Lightning Network – fast, cheap, global bitcoin payments – to applications. In addition, Spiral’s wildly successful grant program supplies funding to dozens of FOSS (free and open-source) bitcoin developers, designers, PMs, and educators all around the world. .
The Role
We’re looking to grow the six-person engineering team that exclusively works on developing the Lightning Development Kit (LDK).
LDK is a comprehensive open-source project that lets developers efficiently build Lightning applications. It includes a full implementation of the Lightning Network protocol written in Rust, APIs, language bindings, demo apps, and more. LDK is used by dozens of projects worldwide, including Lightspark, Cash App, Alby, and BitKit.
The LDK engineers who work for Spiral spend significant time writing code, reviewing code, answering questions, writing documentation, and accepting sensible patches and pull requests from other contributors. LDK aims to build a sustainable open-source project that is welcoming to newcomers, beneficial to users, and ultimately not reliant on a single funding source. The development roadmap is transparent, and corporate priorities do not come first; users do.
You Will
Contribute to LDK by writing and reviewing code, improving testing infrastructure, and assisting projects and companies that use LDK
Help add and maintain features such as the following:
Language bindings, including Java/Kotlin, C#, JavaScript/WASM/browser extensions, and Swift
Support for splicing and dual-funded channels
Support for Taproot, including musig, PTLCs, multi-sig scripts, and custom scripts
Improve the performance, scalability, and robustness of LDK
BOLT 12, VSS, and anchor outputs
A server version of LDK
When you’re not doing all of that, you’ll improve bitcoin through passion projects of your choosing. Almost anything goes.
You Have
8+ years of professional experience
Hands-on experience with bitcoin and the Lightning Network
Experience programming with Rust, C, or C++
Ability to thrive in ambiguity and build creative solutions to complex problems
Appreciation for bitcoin
How to Apply
Include a link to your GitHub (if you’ve got one), any side projects you’ve got floating around that you think we should see, and some words that explain why you’re a fit for this position.
We’re working to build a more inclusive economy where our customers have equal access to opportunity, and we strive to live by these same values in building our workplace. Block is a proud equal opportunity employer. We work hard to evaluate all employees and job applicants consistently, based solely on the core competencies required of the role at hand, and without regard to any legally protected class.

We believe in being fair, and are committed to an inclusive interview experience, including providing reasonable accommodations to disabled applicants throughout the recruitment process. We encourage applicants to share any needed accommodations with their recruiter, who will treat these requests as confidentially as possible. Want to learn more about what we’re doing to build an inclusive workplace? Check out our Inclusion & Diversity page
Application Guidelines
Candidates may submit up to 9 active applications within a 60-day period. Reapplications to the same role are accepted 90 days after a previous application has been reviewed.
Use of AI in Our Hiring Process
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Every benefit we offer is designed with one goal: empowering you to do the best work of your career while building the life you want. Remote work, medical insurance, flexible time off, retirement savings plans, and modern family planning are just some of our offering. Check out our other benefits at Block.
Block, Inc. (NYSE: XYZ) builds technology to increase access to the global economy. Each of our brands unlocks different aspects of the economy for more people. Square makes commerce and financial services accessible to sellers. Cash App is the easy way to spend, send, and store money. Afterpay is transforming the way customers manage their spending over time. TIDAL is a music platform that empowers artists to thrive as entrepreneurs. Bitkey is a simple self-custody wallet built for bitcoin. Proto is a suite of bitcoin mining products and services. Together, we’re helping build a financial system that is open to everyone.
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