Senior Software Engineer, PKI & Cryptographic Systems

About Us

At Cloudflare, we are on a mission to help build a better Internet. Today the company runs one of the world’s largest networks that powers millions of websites and other Internet properties for customers ranging from individual bloggers to SMBs to Fortune 500 companies. Cloudflare protects and accelerates any Internet application online without adding hardware, installing software, or changing a line of code. Internet properties powered by Cloudflare all have web traffic routed through its intelligent global network, which gets smarter with every request. As a result, they see significant improvement in performance and a decrease in spam and other attacks. Cloudflare was named to Entrepreneur Magazine’s Top Company Cultures list and ranked among the World’s Most Innovative Companies by Fast Company.

At Cloudflare, we’re not looking for people who wait for a polished roadmap; we’re looking for the builders who see the cracks in the Internet that everyone else has simply learned to live with. We value candidates who have the instinct to spot a "normalized" problem and the AI-native curiosity to create a solution using the latest tools. Our culture is built on iteration, leveraging AI to ship faster today to make it better tomorrow, while ensuring that every improvement, no matter how small, is shared across the team to lift everyone up. If you’re the type of person who values curiosity over bureaucracy, and that AI is a partner in solving tough problems to keep the Internet moving forward, you’ll fit right in.

Available Locations: Austin, London, or Lisbon (Hybrid)

About the role

TLS is the connective tissue of the Internet, and Cloudflare terminates a large fraction of it. Every day our network handles tens of millions of certificate operations across products like Universal SSL, SSL for SaaS, Origin CA, Cloudflare Access, and Cloudflare Tunnel — and the WebPKI ecosystem underneath all of it is undergoing its largest structural change in a generation: shorter certificate lifetimes, a shift toward post-quantum-safe signature algorithms, and new automation and trust-establishment mechanisms on the horizon.

We are investing in the next generation of Cloudflare’s PKI and cryptographic infrastructure to keep up with, and stay ahead of, that shift. As a Senior Software Engineer on this team, you will design and build the systems that manage certificate lifecycles, protect and use private keys at scale, integrate with hardware security modules, automate issuance and renewal, and take Cloudflare’s cryptographic stack into the post-quantum era. You will work at the intersection of applied cryptography, distributed systems, and security engineering — on infrastructure that a large fraction of the Internet quietly depends on.

This is an early-days role on a growing team. The design decisions you make in the first year will shape how Cloudflare’s certificate and key infrastructure operates for years to come.

Responsibilities

Design and build core PKI systems — certificate lifecycle management, X.509 issuance and validation logic, key parameter enforcement, and policy engines aligned with industry standards including CA/Browser Forum guidance and browser root program policies.

Own the cryptographic core. Integrate with FIPS 140-2 Level 3 (and, where required, Level 4) HSMs via PKCS#11 and vendor-native SDKs; build key ceremony and key-lifecycle tooling; enforce strict key-usage boundaries in code.

Automate at scale. Build and evolve ACME-based issuance and renewal pipelines, short-lived certificate rotation, and revocation mechanisms that serve at Cloudflare’s global scale.

Instrument transparency and audit trails. Integrate with Certificate Transparency, build append-only tamper-evident logging, and design evidence pipelines that hold up to rigorous third-party audit.

Maintain accreditation and respond to a changing compliance landscape. PKI operations must maintain compliance under CA/B Forum, WebTrust, and root stor