Member of Technical Staff - Security Engineering

The role

We build the control chain that powers on, monitors, updates, and protects devices and racks across bare metal, RTOS, and embedded Linux. We also build the communication mechanisms that connect devices to each other and to the host. Security runs through all of it. A chain of trust from the hardware up to the rack management plane: the root of trust each controller boots from, the signed updates that reach the fleet safely, the identity that lets a device prove what it is, the authenticated channels the controllers and devices talk over, and the runtime protections that keep the host Linux kernel and the on-die firmware trustworthy long after boot. These are the layers that let operators rely on the hardware.

You’d be deeply involved in that security across the chain, making it real in software. You’ll work hand in hand with our architecture and hardware teams, bringing the software and system-level view: turning threat models into concrete mechanisms in bare metal, RTOS, and Linux, then designing, prototyping, and validating them. Some of the calls in this model are still open, and you’ll help shape them.

We want engineers who understand security from the inside out. You know how the root of trust, boot chain, key hierarchy, and secure interconnects actually work under the hood, not just how to switch them on. In this role, the security of your software solutions depends entirely on how well you understand the hardware beneath it. Some of the protections we rely on live in silicon, some in software, and part of the skill is knowing which belongs where. We’re looking for people who know both sides well enough to build the mechanisms that close whole classes of bugs by design.

We’re not heavy on levels here! Whether you’d call yourself senior, staff, principal, or lead, what matters is depth of security judgement, system-level experience, and working well with the engineers around you. If you’ve worked deep in the security of real systems and like to get your hands on the code and the systems around it, we’d like to hear from you.

What you’ll do

• Shape the security of the control chain (device, board, chassis, and rack controllers): threat models, trust boundaries, and a coherent secure-by-design approach across all platforms

• Design and help build secure boot and the root of trust on each controller: verified/measured boot, signing and verification, anti-rollback, and locking down debug and privileged access in production

• Secure the interconnects, between controllers and between devices and the host, with authentication, integrity, and additional protections where needed

• Design and build the cryptographic mechanisms: key hierarchies, provisioning and storage, device identity, and remote attestation so the fleet can prove what it’s running

• Make firmware updates safe end to end: signed images, rollback protection, staged rollout, and clean recovery, across every hop of the chain

• Protect the running system, not just boot: harden the host Linux kernel and the on-die firmware

• Work closely with hardware and the rest of the software team to build security into the product, running threat-model reviews, triaging vulnerabilities, and driving fixes to closure

What we’re looking for

We expect you to know the fundamentals, and to have real, practical experience across several of these:

• An adversarial mindset and sharp threat-modeling instincts: trust boundaries, assets, attacks, and honesty about residual risk

• Hands-on experience with the core security primitives in software and in silicon: secure boot, root of trust, cryptography, and key management, including how they’re implemented and where they can fail

• Secure protocol and channel design between components

• Strong C and Rust, and the instinct for memory safety and defensive coding that low-level security work needs

• Experience building, not just using, security mechanisms: a secure-boot chain, key hierarchy, or attestation flow you shaped

That’s the core. We get especially curious about your application when you also bring some of the following. Very few candidates tick every box here, and we don’t expect you to:

• Attestation at boot and at runtime, and management-plane protocols (DICE, IETF RATS, SPDM, MCTP, PLDM; confidential-computing directions like TDISP)

• Hardware building blocks and firmware/Linux hardening (HSM, TPM, secure element, Caliptra, secure debug; open firmware/boot projects, image minimisation)

• Assurance and resistance (supply-chain security with SBOM and SLSA, fuzzing and testing, standards like NIST 800-series, Common Criteria, OCP incl. S.A.F.E., TCG/DMTF; physical and side-channel awareness)

• AI/LLM-assisted security tooling, and RISC-V / GPU / ML-accelerator experience

What We Offer

• Competitive salary: A competitive salary reflective of your experience and the specialist nature of the role.

• Equity & Ownership: meaningful equity so everyone shares in the value creation

• Benefits: Private Medical, Dental and Vision, Contributory Pension, 25 Days holiday plus bank holidays and Life/Critical Illness Insurance.

• Diverse & fun office: we believe the hardest problems get solved by the broadest range of minds. We are committed to Equal Employment Opportunity through attracting and retaining a diverse team and building an inclusive environment.

Fractile is seeking to increase the clock speed of global progress, one chip at a time. We’ve recently raised $220M from investors including Founders Fund and Accel and our most important work lies ahead. Join us!

Export controls

Our work involves technologies subject to UK, US and other international export control regulations. Certain roles may require additional eligibility checks to ensure compliance with applicable law. We'll be transparent about this throughout the hiring process.