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Agent guide: [/agents.md](https://www.wearedevelopers.com/agents.md). --- # Senior Software Developer - C - **Company:** Cavero Quantum - **Location:** Leeds, UK (Remote available) - **Experience:** Expert - **Salary:** £60,000.0 - £75,000.0 - **Contract:** Permanent contract - **Skills:** Aliasing, ARM Architecture, C++ (Programming Language), Cloud Computing Security, Static Program Analysis, Code Review, Continuous Integration, Software Debugging, Linux on Embedded Systems, Federal Information Processing Standards (FIPS), Fuzz Testing, MISRA C (C Programming Language), Network Architecture, Program Analysis, Smart Cards, Software Engineering, Toolchain, Agentic-AI, Low Latency, Build Tools, Programming Languages - **Published:** October 5, 2026 - **Apply:** https://www.indeed.com/viewjob?jk=87caf866b81e1ce4 ## About the Role * C at depth - Substantial professional experience writing production C - not C++ with a C accent. Fluency with the standard at a language-lawyer level: undefined behaviour, aliasing, alignment, integer promotion, and how your compiler actually treats them. * Optimisation - A track record of making software materially faster or smaller in a commercial setting. You can profile, read the generated assembly when it matters, and reason about cache, memory, and instruction cost. * Constrained environments - Experience delivering into environments with hard limits on memory, storage, power or latency - embedded systems, secure elements, real-time platforms, network infrastructure, or high-throughput media systems. * Security engineering - Demonstrable care for security in code: threat awareness, defensive implementation, secure handling of keys and secrets, and experience with cryptographic libraries, secure boot, content protection, or comparable protective mechanisms. * Systems and toolchains - Confident with cross-compilation, build systems, debuggers, static and dynamic analysis, and continuous integration against hardware. * Testing rigour - You treat testing of security-critical code as part of the design, not a phase afterwards. * Autonomy - Comfortable being the senior technical voice in a small company, taking a sparse specification, and turning it into shipped, defensible software. Desirable skills and experience * Prior work on cryptographic implementations, whether primitives, protocol stacks, or hardware-accelerated crypto. * A background in any domain where performance, footprint, and security must be solved together. Media delivery and DRM, telecoms, and network infrastructure, automotive, and industrial control, payments and smart cards, defence and avionics, or real-time and high-throughput systems generally - we are interested in the engineering discipline rather than the sector it was learned in. * Familiarity with post-quantum cryptography and the NIST standards (ML-KEM, ML-DSA, SLH-DSA) is useful, but we can teach the post-quantum part to the right engineer. * Experience with formal assurance regimes: FIPS 140-2/3, Common Criteria, GlobalPlatform, GSMA eSIM, or defence security standards. * SIM, eSIM, smart card, secure element, TEE, or HSM development experience. * Assembly-level optimisation on ARM Cortex-M or similar; hardware crypto accelerator integration. * Exposure to telecoms, satellite communications, defence, or industrial IoT deployment. * Experience with Agentic AI and cloud security. * Experience in other programming and scripting languages. * Ability to work autonomously and influence development direction., * Are you comfortable working in a hybrid setting? * Are you willing to undergo a background check in accordance with local law/regulations? * Do you have experience working in constrained environments with C? Experience: * Software development: 5 years (required) Language: * English (required) ## Description What makes this engineering problem interesting is the constraint. Our library can run in under 2.1KB and performs key establishment at roughly twice the speed of the NIST-standardised alternative, enabling strong post-quantum cryptography on SIMs, eSIMs, and IoT sensors that cannot host anything else. It is crypto-agile, supports all standard encryption methods, and is defined as a locked-down module boundary for independent FIPS 140-3 assessment., As our Senior Software Developer, you will own the implementation of Cavero's cryptographic software in C - the primitives, protocol implementations, and platform ports that make up CaveroCore and the products built on it. You will work directly with our Lead Cryptographer and Cryptography team, translating formal designs and reference implementations into code that is small, fast, constant-time, and defensible under audit., Cryptographic implementation * Implement, optimise, and maintain Cavero's encryption, hashing and random number generation primitives in C, working from formal specifications and the cryptography team's reference implementations. * Implement and harden the CaveroKEX key exchange and CaveroCTX continuous verification protocols across supported platforms. * Write constant-time, side-channel-resistant code, and demonstrate that it is - no data-dependent branching or memory access in secret-dependent paths. * Maintain crypto-agility: keep algorithm selection pluggable so customers can adopt new schemes without re-architecting. Performance, footprint and portability * Drive down code size, RAM usage, and cycle count against agreed budgets on constrained targets - SIM and eSIM secure elements, IoT microcontrollers, and embedded Linux. * Profile, benchmark, and instrument the codebase; establish the performance baselines and regression gates the team uses for validation. * Port and validate CaveroCore across toolchains, architectures, and endianness, including cross-compilation and bare-metal targets. * Make and document the trade-offs between speed, footprint and assurance, and defend them to customers and assessors. Security assurance and quality * Build and maintain the test infrastructure for cryptographic code: known-answer tests, fuzzing, sanitisers, static analysis, and continuous integration on real target hardware. * Prepare the codebase for an independent FIPS 140-3 assessment: module boundary discipline, evidence, traceability, and documentation. * Lead code reviews for security-critical changes and set coding standards (for example, MISRA-style discipline where it earns its place). * Manage secure development practices: dependency hygiene, reproducible builds, secret handling, and release integrity. Delivery and collaboration * Deliver against pilot commitments with named customers in telecoms, defence, and satellite communications - this work ships, and the dates are real. * Work alongside the Product Owner and Head of Engineering to size work, shape the backlog, and keep the roadmap honest about what is achievable. * Support integration with partner platforms and provide senior technical input to customer and pre-sales conversations where deep implementation detail is needed. * Mentor developers and raise the team's cryptographic engineering standard.