Senior Security Engineer

Job description

ABOUT PROJECT ELEVEN Project Eleven is an applied lab of builders and technologists working at the intersection of quantum computing and cryptography. We build impactful solutions that push the digital-asset ecosystem to a more secure future. Our focus is post-quantum migration: upgrading wallets, identity, and settlement rails to quantum-safe primitives without breaking UX, composability, and developer workflows. Our mission is to future-proof digital assets and preserve self-sovereignty in a post-quantum world. We do that by building the canonical tooling and products teams can adopt: crypto-agile infrastructure, reference implementations, and integrations that fit real constraints like latency, cost, compatibility, key rotation, and recovery. We work with leading ecosystems to make this migration real through products we build, audits, testnets, and cutting edge research. The vision we are have is clear: a proven upgrade path, production-ready tooling and users retaining control of their assets and identity, before CRQC exists. THE ROLE We're hiring a Senior Security Engineer to own the security engineering of our institutional product and platform. This is a hands-on, build-it-yourself role: you'll threat model our systems, design and implement secure architecture, harden our AWS infrastructure, own security of key management (including HSMs and TEEs), secure our supply chain and build pipeline, and run incident response. You'll work directly in our codebase and infrastructure alongside engineering with security as a key focus. This role is a full-time, fully remote position in Europe (GMT to GMT+2). WHAT YOU'LL BE RESPONSIBLE FOR - Threat modelling & secure architecture: lead threat modelling for new and existing systems, and shape the architecture of our institutional product so security is designed in, not bolted on - Application security: build out our AppSec program: secure code review, secure SDLC, dependency and vulnerability scanning, security testing in CI - Infrastructure hardening & AWS security: harden our cloud infrastructure and deployment pipeline; own AWS security posture (IAM, network segmentation, secrets, logging/detection) - Key management, HSMs & TEEs: design, develop, and operate our key management architecture, including HSM-backed signing and TEE-based isolation for sensitive operations - Reproducible builds & supply chain security: implement reproducible/verifiable builds and harden our software supply chain (dependency provenance, build integrity, artifact signing) - Security reviews: review designs, code, and cryptographic protocols/integrations across our backend systems, partnering closely with engineering rather than gating them - Incident response: build and run our incident response capability: runbooks, on-call rotation, postmortem culture - Compliance support: collaborate with the team driving our compliance program (SOC 2 Type II as the first milestone), owning the technical controls and evidence without owning the program itself WHAT YOU BRING - 5+ years in security engineering with hands-on ownership of building and securing production systems - Strong software engineering ability. You can read, write, and review production code and infrastructure-as-code, not just point out issues in it - Strong applied cryptography knowledge: key management, signing protocols, secure key handling at rest and in use - Hands-on experience hardening cloud infrastructure (AWS) and modern deployment platforms - Real threat modelling experience and the ability to make pragmatic risk tradeoffs in a fast-moving startup environment - Experience with secure architecture and design review for distributed or backend systems - Strong English communication, including the ability to explain security engineering clearly to engineers, customers, and auditors WHAT WE'D LOVE TO SEE - Direct experience with HSMs, TEEs (SGX/SEV/TrustZone/Nitro), and/or MPC/threshold signing in production - Experience implementing reproducible builds or software supply chain security (SLSA, sigstore, artifact provenance) - Background in institutional digital-asset infrastructure: custody platforms, exchanges, HSM-backed systems, or regulated financial infrastructure - Familiarity with post-quantum cryptography and the operational implications of migrating cryptographic primitives - Experience running incident response for a security-critical product - Prior experience as the first security engineer at a startup, or building a security function from scratch - Offensive security background (red team, pentesting, vulnerability research) as a complement to defensive work - Open-source contributions to security tooling, cryptography, or related infrastructure - Exposure to SOC 2, ISO 27001, or equivalent compliance frameworks (nice to have, not the core of the role) EQUAL OPPORTUNITY We are committed to equal employment opportunity and believe that diverse teams build better products. All qualified applicants will receive consideration without regard to any protected characteristic under applicable law.