Senior Cryptography Engineer - C developper
Confirmed on the employer's own hiring board on Oct 16, 2026. First seen by Alion on Sep 14, 2026.
Who we are
CryptoNext Security is a Paris-based start-up founded in 2019, building on more than 20 years of academic research. CryptoNext is a software vendor specializing in quantum-computer-resistant cryptography (PQC: post-quantum cryptography). Its software suite, the Quantum Safe Remediation Suite, includes the world-reference Quantum Safe Library (C-QSL), covering the full selection of NIST algorithms, and helps enterprises and integrators migrate to the era of post-quantum cybersecurity.
CryptoNext Security was cited among the 5 reference leaders in Gartner’s report on post-quantum cryptography (October 2021) and received the Innovation Prize at «Les Assises 2022». CryptoNext is a member of Campus Cyber, Hexatrust and Systematic, and was selected in 2022 to join a workgroup of the US National Cybersecurity Center of Excellence (NCCoE) dedicated to PQC migration best practices.
We are looking for a highly motivated, senior Cryptography R&D Engineer to join our team and take ownership of a key strategic project: porting our post-quantum cryptographic library across multiple platforms, with a particular focus on hardware/software FPGA accelerators. This role sits at the intersection of cryptography, low-level C engineering and embedded/hardware design.
On a daily basis, you will
- Design and implement efficient C code for post-quantum cryptographic algorithms (NIST-selected or recommended by EU agencies), balancing performance, portability and security.
- Port and optimize the CryptoNext Quantum Safe Library (C-QSL) across multiple platforms and architectures
- Adapt implementations for constrained and embedded environments (e.g., IoT, Cortex-M, embedded Linux).
- Define and run test and validation strategies (functional, performance, security) across all target platforms.
- Support security certification processes (CSPN, Common Criteria, FIPS) for the ported implementations.
- Document your work through technical reports and, where relevant, scientific papers.
- Collaborate closely with the R&D team and cross-functional teams to solve complex technical challenges.
The CryptoNext Quantum Safe Library is developed mainly in C and Assembly, targeting several operating systems (Linux, Windows, iOS, Android…) and processor architectures (x86, Arm, RISC-V…), as well as FPGA-based hardware accelerators.
Other tasks may include, depending on your profile and the product roadmap: work on side-channel countermeasures, and collaboration with the team in charge of integrating the library with communication protocols and cryptographic objects (TLS, IPsec, PKCS#11, X.509…) in post-quantum or hybrid mode.
Requirements
The skills you will demonstrate
- Significant, senior-level experience in cryptography engineering, ideally 5+ years, gained in a software company or department of a larger organization (cybersecurity vendor, IT application or hardware provider), ideally with international teams or clients.
- Engineering degree or Master’s in computer science, mathematics or a related field; a PhD in cryptography or a related discipline is a strong plus.
- Solid foundations in algorithmics and algebra, with the ability to translate mathematical constructs into efficient, correct implementations.
- Strong programming skills in C; comfort working close to the hardware and optimizing for performance and security.
- Comfort using embedded development and hardware debugging tools (GCC, GDB, QEMU, JTAG…) and practical experience with source code management and continuous integration using GitLab CI.
- Experience with public-key cryptography, symmetric-key cryptography, hash functions, and cryptographic protocols/frameworks such as OpenSSL is a plus.
- Experience in one or more of the following is a strong plus: embedded software development, hardware/software co-design, FPGA implementation.
- Good French & English communication skills, both oral and written.
Benefits
What's in it for you at CryptoNext
- Ownership of a strategic, high-impact technical challenge - multi-platform porting and hardware acceleration - at the heart of our product roadmap.
- A fast-growing, globally recognized deep-tech start-up, named among Gartner’s 5 reference leaders in post-quantum cryptography.
- Full-time position, based in Paris.
- Competitive salary, commensurate with experience.