Senior Cryptography Engineer - C developper

AVP; Paris; On-site; EUR 110,000 - 160,000; Full time

Job summary

CryptoNext Security in Paris seeks a senior Cryptography R&D Engineer to port the Quantum Safe Library across platforms, with a focus on hardware/software FPGA accelerators and secure implementations.

You will design and optimize C code for post-quantum algorithms, work on embedded environments (IoT, Cortex-M, embedded Linux), and collaborate with global R&D teams to meet certification standards and integrate with TLS, IPsec, and other cryptographic objects.

Qualifications

• Senior level cryptography engineering experience, 5+ years.
• Engineering degree or higher in CS/math or related field; PhD beneficial.
• Strong C programming skills and hardware-aware optimization.

Responsibilities

• Design and implement efficient C code for post-quantum algorithms.
• Port and optimize the Quantum Safe Library across platforms with FPGA focus.
• Contribute to hardware/software co-design and evaluate FPGA trade-offs.
• Adapt implementations for constrained embedded environments (IoT, Cortex‑M).
• Define test/validation strategies and support certifications (CC, FIPS).
• Document work and collaborate with global R&D teams.

Skills

Cryptography

C programming

Embedded HW

GCC/GDB

CI/CD

OpenSSL

FPGA experience

Education

Engineering degree

Master’s in CS/Math

PhD in cryptography

Tools

Quartus Prime

Vivado

QEMU

GDB

JTAG

OpenSSL

Job description

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, with an emphasis on hardware/software FPGA accelerators.
• Contribute to hardware/software co-design: specify and prototype cryptographic accelerators, evaluate trade-offs between software and FPGA-based implementations.
• 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.

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.
• Exposure to FPGA development using Intel (Altera) or AMD (Xilinx) devices, including familiarity with the associated EDA tools (Quartus Prime, Vivado), would be considered a plus.
• Good French & English communication skills, both oral and written.

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.