Senior Applied Cryptography Engineer (80–100%)

Threema; Freienbach; Hybrid; CHF 140.000 - 210.000; Vollzeit

Benefits dieser Stelle

Flexible working hours

Work from home up to 2 days per week

Work from anywhere for two weeks per/2

Own hardware: macOS or Linux

Public transport discount or parking

Fitness room and monthly trainer

Professional massage monthly

Language courses (German/English)

Coffee machine

Regular company events

Zusammenfassung

Threema is seeking a Senior Applied Cryptography Engineer to design, build, and scrutinize cryptographic protocols behind our messenger, contributing to the privacy of millions of users.

You will lead protocol design, quantum-safe migration with IBM Research, threat modeling, and security analysis of protocols and implementations, while collaborating with product and engineering teams.

Qualifikationen

• Degree in computer science, mathematics, or information security, ideally with a focus on cryptography, or equivalent practical experience.
• Solid understanding of modern cryptographic primitives (AEAD, key exchange, KDFs, digital signatures) and how they fail when combined.
• Working knowledge of key encapsulation mechanisms and post-quantum cryptography, including hybrid constructions such as X25519MLKEM768.
• Experience designing or reviewing security protocols, ideally in end-to-end encryption, key agreement, or multi-device settings.
• You write code yourself, in Rust, Kotlin, Swift, TypeScript, or similar.
• Experience reviewing implementations for side channels, nonce reuse, misuse-prone APIs, etc.
• Nice to have: hybrid post-quantum handshakes, formal protocol verification, published research, CVEs, vulnerability disclosure.

Aufgaben

• Design, build, and scrutinize cryptographic protocols for our messenger.
• Lead migration to quantum-safe cryptography in collaboration with researchers at IBM Research.
• Own threat modeling for new product features and protocol designs with product and engineering teams.
• Analyze protocols, algorithms, and implementations for security weaknesses and attack vectors.
• Coordinate with bug-bounty reports and engineering teams to address issues.
• Follow developments in applied cryptography and translate findings into product improvements.

Kenntnisse

Cryptography

Security engineering

Protocol design

Rust

Kotlin

Swift

TypeScript

Side-channel analysis

English (B2)

Ausbildung

CS/Math/InfoSec degree

Jobbeschreibung

Senior Applied Cryptography Engineer (80–100%)

Your Role

As an applied cryptography engineer at Threema, you will help us design, build, and scrutinize the cryptographic protocols behind our messenger, and contribute to the effective privacy protection of millions of people.

Your Tasks

Protocol design and quantum-safe migration:

• Develop and specify cryptographic communication protocols
• Design cryptographic systems, such as key management and multi-device synchronization
• Lead Threema’s migration to quantum-safe cryptography, together with the cryptography researchers at IBM Research
• Own threat modeling for new product features and protocol designs, in close collaboration with the product and engineering teams

Security analysis:

• Analyze protocols, algorithms, and implementations for security weaknesses, and assess what new attack vectors mean for our products
• Assess the vulnerability reports that reach us through our bug-bounty partner and coordinate the fix with the engineering teams

Research and community:

• Follow current developments in applied cryptography and turn relevant findings into concrete product improvements
• Maintain contacts with the security research community and, if you enjoy it, represent Threema at conferences

Your Skills

Cryptography and engineering:

• Degree in computer science, mathematics, or information security, ideally with a focus on cryptography, or equivalent practical experience
• Solid understanding of modern cryptographic primitives (AEAD, key exchange, KDFs, digital signatures) and of how they fail when combined incorrectly
• Working knowledge of key encapsulation mechanisms and of post-quantum cryptography, including hybrid constructions such as X25519MLKEM768
• Experience designing or reviewing security protocols, ideally in end-to-end encryption, key agreement, or multi-device settings
• You write code yourself, in at least one of Rust, Kotlin, Swift, TypeScript, or something comparable
• Experience reviewing implementations for side channels, nonce reuse, misuse-prone APIs, and similar problems
• Nice to have: practical experience with hybrid post-quantum handshakes, formal protocol verification, published research, or CVEs, experience with coordinated vulnerability disclosure

Experience with AI tools:

• You’re familiar with current frontier AI models and use them as a productivity multiplier in design work as well as in coding, for example to review specification drafts, survey recent literature, or poke holes in a protocol design
• Whatever tools you use, the outcome is yours; AI can draft and suggest, but the person accountable for a protocol that holds is you

Soft skills:

• Strong sense of responsibility, precise way of working
• You can write a protocol specification that someone else can implement, and explain a cryptographic trade-off to people who are not cryptographers
• Pragmatic judgment about when a design is good enough to ship and when it is not
• Willingness to have your own designs picked apart, and to pick apart other people’s with care
• Good written and spoken English (at least B2), German is a nice-to-have

We are also happy to accept applications from people who meet many but not all of these criteria.

What We Offer

• A young, motivated team with straightforward communication
• Flexible working hours, option to work from home up to two days per week
• Option to work from anywhere for two weeks per year
• Option to take unpaid leave
• You can choose your own hardware (macOS or Linux)
• Public transportation discount or parking space (electric car charging available)
• Free use of fitness room, including a fitness trainer once a month
• Professional massage once a month
• Internal German or English courses
• A great coffee machine ;-)
• Regular company events and aperitifs
• The good feeling of contributing to the effective protection of the privacy of millions of people

Place of work:

Pfäffikon SZ (Greater Zurich Area)

Start date

Immediately or by agreement

Have we sparked your interest?

We believe that diverse teams build better products. We welcome and encourage applications from people of all backgrounds, and perspectives. Your unique experience is an asset, and we’d love to hear from you.