Senior Software Engineer, Bitcoin Wallet (Bitkey)

Block is one company built from many blocks, all united by the same purpose of economic empowerment. The blocks that form our foundational teams — People, Finance, Counsel, Hardware, Information Security, Platform Infrastructure Engineering, and more — provide support and guidance at the corporate level. They work across business groups and around the globe, spanning time zones and disciplines to develop inclusive People policies, forecast finances, give legal counsel, safeguard systems, nurture new initiatives, and more. Every challenge creates possibilities, and we need different perspectives to see them all. Bring yours to Block.

The Role

Bitkey is Block’s Bitcoin self-custody wallet, built to make it safe and easy for people everywhere to hold their own Bitcoin. Our team is building a product that delivers best-in-class security and usability to a market where people have historically had to sacrifice one for the other. We’re finding ways to break those tradeoffs, bridging cryptography with simple, everyday experiences. It’s a hard problem — and if that motivates you, you’ll be in good company at Bitkey.

We’re looking for a Senior Software Engineer who is passionate about Bitcoin and wants to shape the future of self-custody. This role will play a key part in creative innovations in the self custody space while building out platform libraries and services that power Bitkey. You’ll help build the secure foundations that our mobile clients and customer experiences rely on.

Candidates may come from backend, platform, or even mobile backgrounds, but success in this role requires deep experience with Bitcoin protocols applied in production and strong engineering fundamentals.

You’ll join a mission-driven team that values curiosity, creativity, and collaboration. You’ll help us solve real customer problems: protecting funds, enabling recovery, balancing usability with security. You’ll also explore innovative unlocks using Bitcoin’s building blocks to open up new customer capabilities, recovery paradigms, and security techniques.

You Will

• Design, build, and maintain secure backend services and libraries that enable safe and usable Bitcoin self-custody.
• Create platform primitives and APIs that mobile apps and external clients can rely on.
• Work across boundaries — from cryptographic protocols, to custody flows, to integration with mobile experiences, with a bias toward pragmatic problem-solving.
• Collaborate closely with product managers, designers, and other engineers to deliver solutions that balance usability, availability, and security.
• Take end-to-end ownership of projects, from ideation through execution.

You Have

• A deep interest in Bitcoin and conviction about the importance of self-custody.
• Proven experience shipping production Bitcoin software, or deep protocol expertise with a desire to build for customers, whether from a backend, custody, or mobile background.
• Baseline understanding of secure key management and recovery problems.
• Strong engineering fundamentals and comfort moving across stacks and languages (we use Rust and Kotlin, and can help you learn them if they’re new to you).
• A track record of collaborating in cross-functional teams and contributing beyond just code.
• Curiosity, creativity, and a drive to innovate in service of real customer needs.

Nice to Have

• Familiarity with applied cryptographic techniques in Bitcoin custody.
• Experience building SDKs, APIs, or libraries consumed by mobile apps.
• Contributions to open-source Bitcoin projects.
• Experience with security-sensitive or correctness-critical systems

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 an equal opportunity employer evaluating all employees and job applicants without regard to identity or any legally protected class. We will consider qualified applicants with arrest or conviction records for employment in accordance with state and local laws and "fair chance" ordinances. 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