Sthenos

EFA GROUP comprises companies in Aerospace, Security, Defense, and Industrial Cooperation with a solid international presence. EFA GROUP currently employs more than 400 people, the majority of whom are engineers and scientists. Headquartered in Greece, the Group maintains a strong international presence across Europe (Cyprus, Belgium, Switzerland, Estonia, and Germany), Asia (Singapore, Indonesia, and South Korea), the Middle East (UAE), and the United States, serving customers in 34 countries worldwide. 

The GROUP  includes EFA VENTURES (Supply Chain Management and integrated services), AEROSPACE VENTURES (Industrial Participation and related services), SCYTALYS (Systems Integration and Software), ES SYSTEMS (MEMs & IoT Integration), EPICOS (Global Defense B2B Information Platform), UCANDRONE (Unmanned Systems), AETHER AERONAUTICS (Target Drones), STHENOS AI (Intelligence Solutions), THYREOS CYBER (cyber security), SUPERIOR AIR (aviation services and specialized aerial missions), SSMART (defense hardware - software production and services). 

STHENOS AI is the AI developer of EFA Group, building intelligent, mission-ready solutions for defense and aerospace. With deep expertise in Command-and-Control (C2), cyber defense, computer vision, and autonomous systems, we design and deploy secure, field-proven AI that enhances operational efficiency and situational awareness. As part of a leading European defense ecosystem, we bring scalable innovation where it matters most - in the theater of operations. Internally, we are building a unified operations platform: a single system through which the entire company will run its daily work, with AI woven through every workflow. We have validated the concept with a working prototype and are now assembling a small senior team to build the production platform properly, from the ground up.  

The Role

STHENOS AI is looking for a Senior Cryptography Engineer to design, implement and maintain cryptographic infrastructure for defense and dual-use applications. The role focuses on public-key infrastructure (PKI), hardware security modules (HSMs), key management and secure communications.

This is a hands-on engineering position for professionals with experience in cybersecurity, PKI, key management or cryptographic software integration. You will work closely with our platform engineering and quantum technologies teams to develop reusable security architectures and support the gradual adoption of post-quantum cryptography (PQC).

We are looking for someone with proven experience delivering cryptographic systems, strong security judgment and an interest in developing expertise in PQC. Previous experience in quantum technologies or PQC is an advantage, but not required. The focus of the role is on integrating, implementing and evaluating established cryptographic technologies rather than developing new cryptographic algorithms.

Key Responibilities

• Design and integrate cryptographic components and secure communication services, defining trust boundaries, authentication mechanisms, and key management interfaces
• Implement and operate PKI services, including certificate issuance, renewal, revocation, trust-chain validation, and certificate lifecycle automation
• Integrate HSMs and key management services, ensuring appropriate controls for key generation, storage, access, backup, recovery, rotation, and destruction
• Develop and review integration code and deployment automation, and troubleshoot, test, harden, and maintain cryptographic services in collaboration with platform and software engineers
• Build reproducible demonstrators and crypto-agile configurations, supporting controlled algorithm changes, credential updates, verification, and rollback
• Evaluate Post-Quantum Cryptography (PQC) integration in collaboration with the quantum technologies team
• Design, implement, and maintain automated cryptographic discovery and Cryptographic Bill of Materials (CBOM) pipelines, integrating them into CI/CD workflows and scheduled scans
• Maintain up-to-date CBOMs across software releases and deployed-system changes, tracking algorithms, parameters, libraries, protocols, certificates, key metadata, and dependencies
• Validate cryptographic coverage and report changes to support security reviews and migration planning
• Develop repeatable functional, interoperability, and performance tests, and support independent security assessments and remediation activities
• Maintain architecture documentation, configuration baselines, validation evidence, and operational runbooks to support certification and system accreditation activities

Requirements

• Degree in Computer Science, Cybersecurity, Engineering, Mathematics, or a related technical field, or equivalent professional experience
• Hands-on experience delivering cryptographic infrastructure, including PKI and HSM integration, with responsibility for implementation and operational outcomes
• Strong applied knowledge of symmetric and asymmetric cryptography, digital signatures, authentication, key lifecycles, and secure random-number generation
• Practical experience with certificate-based security and secure communications, including TLS or mutual TLS, with familiarity with protocols such as IPsec/IKEv2 or SSH
• Experience with secure software development, configuration control, testing, and troubleshooting
• Understanding of relevant assurance requirements and the distinction between algorithm approval, module validation, and system accreditation
• Experience with containerized environments, infrastructure-as-code, cryptographic discovery, or Cryptographic Bills of Materials (CBOMs)
• Ability to work independently, communicate security trade-offs to technical and non-technical audiences, document decisions, and collaborate effectively with internal teams and external specialists
• Eligibility to acquire EU and/or NATO security clearances is mandatory

Nice to Have

• Familiarity with Post-Quantum Cryptography (PQC), including ML-KEM, ML-DSA, or SLH-DSA, and hybrid or crypto-agile deployments
• Previous PQC project delivery experience is highly valued but not essential
• Experience supporting cryptographic module validation, security certification, or formal system accreditation, including preparation of technical evidence for processes such as FIPS 140-3 or Common Criteria evaluations
• Experience working on government or defense projects, dual-use technologies, EDF initiatives, or other multi-partner technical collaborations
• Familiarity with systems and software modelling approaches, including Model-Based Systems Engineering (MBSE) or Model-Driven Engineering (MDE)