Senior Cryptography Engineer - C developper

CryptoNext Security; Paris; Sur place; EUR 90 000 - 120 000; Plein temps

Avantages offerts par ce poste

Strategic technical challenge

Global Gartner reference

Paris-based start-up

Résumé du poste

CryptoNext Security, a Paris-based start-up, seeks a senior Cryptography R&D Engineer to port and optimize the Quantum Safe Library (C-QSL) across platforms, including FPGA accelerators, with a focus on performance and security.

You will work at the intersection of cryptography, low-level C, and embedded hardware, collaborating with international teams, and contributing to CSPN/FIPS readiness and technical publications.

Qualifications

• Significant senior experience in cryptography engineering (5+ years).
• Engineering degree or MSc in computer science, mathematics or related field; PhD is a strong plus.
• Strong programming skills in C; close-to-hardware optimizations for performance and security.

Responsabilités

• Design and implement efficient C code for post-quantum algorithms across platforms.
• Port and optimize the Quantum Safe Library (C-QSL) to multiple architectures, including FPGA accelerators.
• Adapt implementations for embedded environments (IoT, Cortex-M, embedded Linux).
• Define and run functional, performance, and security tests across targets.
• Support security certifications (CSPN, Common Criteria, FIPS) for ported code.
• Document work via technical reports and potentially scientific papers.

Connaissances

Senior cryptography

C programming

Embedded work

GCC/GDB/QEMU

Hardware debugging

OpenSSL experience

French & English

Formation

Engineering degree or MSc in CS/Math

Outils

FPGA

GitLab CI

Description du poste

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.

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