Senior Cryptography Engineer - C Developer

CryptoNext Security

. Design and implement efficient C code for post-quantum cryptographic algorithms selected or recommended by NIST or EU agencies.

Posted 9/15/2026full-timeParis • FranceSeniorWebsite

Core Competencies

Role fit

Core Competencies

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Demonstrates expertise in cryptography engineering with a focus on post-quantum algorithms, efficient C programming, and performance optimization across various platforms. Proficient in security certification processes and collaborative problem-solving within cross-functional teams.

Highest-signal resume keywords

Cryptography EngineeringC ProgrammingPost-Quantum AlgorithmsEmbedded DevelopmentSecurity Certification Processes

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Hard Skills

C ProgrammingAlgorithmicsMathematicsPublic-Key CryptographySymmetric-Key CryptographyHash FunctionsCryptographic ProtocolsFPGA ImplementationPerformance OptimizationSecurity Testing

Soft Skills

Communication SkillsCollaboration

Tools & Technologies

GCCGDBQEMUJTAGGitLab CI

Certifications & Qualifications

Engineering DegreeMaster’s in Computer SciencePhD in Cryptography

Industry Keywords

Post-Quantum CryptographyCortex-MEmbedded LinuxCSPNCommon CriteriaFIPSTLSIPsecPKCS#11X.509

Tech Stack

Tools & technologies

AndroidAssemblyCyber SecurityiOSIoTLinux

About the role

Key responsibilities & impact

Design and implement efficient C code for post-quantum cryptographic algorithms selected or recommended by NIST or EU agencies.
Port and optimize the CryptoNext Quantum Safe Library (C-QSL) across multiple platforms and architectures.
Adapt implementations for constrained and embedded environments such as IoT, Cortex-M, and embedded Linux.
Define and run functional, performance, and security testing and validation strategies across target platforms.
Support CSPN, Common Criteria, and FIPS security certification processes for ported implementations.
Document work through technical reports and, where relevant, scientific papers.
Collaborate with R&D and cross-functional teams to solve complex technical challenges.
Work with C and Assembly implementations targeting Linux, Windows, iOS, Android, x86, Arm, RISC-V, and FPGA-based hardware accelerators.
Potentially work on side-channel countermeasures and integration with TLS, IPsec, PKCS#11, and X.509 in post-quantum or hybrid mode.

Requirements

What you’ll need

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

Comp & perks

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.