Kai Greshake, Developer in Saabrücken, Germany
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Kai Greshake

Verified Expert  in Engineering

Security Testing Developer

Saabrücken, Germany
Toptal Member Since
June 15, 2017

Kai works in the field of IT security. He's a seasoned developer and security consultant. Having worked on projects of all sizes with remote and local teams, Kai can deliver standalone high-performance applications for use in a back-end environment, penetration testing, and general security consultation. Kai's high-quality education in computer science allows him to understand and apply complex subjects efficiently.


Security Testing, IoT Security, Web App Security
Incident Response, Penetration Testing, Security




Preferred Environment

Rust, .NET Core, Linux, Git

The most amazing...

...thing I've created is a neural network trained on quotes from famous people, generating new "wisdom" which self-improves through user feedback.

Work Experience

Pentester | Consultant

2022 - PRESENT
  • Developed highly secure software drivers for industrial computing.
  • Tested products, applications, and infrastructure offensively to help companies improve their security posture.
  • Developed partially automated reporting tools to cut time spent writing penetration testing reports by two-thirds while producing higher-quality output.
Technologies: Security Testing, IoT Security, Web App Security

Cyber Security Engineer | Penetration Tester

2019 - 2021
  • Coached many customers to identify security issues and efficiently fix them.
  • Assisted companies in incident response, responding to attacks and mitigate them.
  • Surveyed industry-standard tooling for vulnerabilities to help customers maintain a secure stance. Identified many issues, including a critical vulnerability in Symantec Critical Systems Protection software which protects industrial plants worldwide.
Technologies: Incident Response, Penetration Testing, Security

Security Researcher

2015 - 2019
Center for IT-Security, Privacy, and Accountability
  • Developed high-performance software for the parallel calculation of advanced anonymity metrics.
  • Analyzed the security of Android apps generated using app generators such as Appy Pie and SeattleCloud.
  • Implemented a fuzzing environment and tools to fuzz the Android middleware.
Technologies: Python, Rust, C++, C, .NET Core

Software Developer

2014 - 2015
KS Software (now xbAV)
  • Developed a financial consultation back-end (calculation of taxes, interest rates, and more).
  • Worked on a UI using WPF for the consultation process.
  • Implemented quality-control measures (unit tests).
Technologies: Visual Studio, Git, Windows Presentation Foundation (WPF), .NET

Freelance Developer

2012 - 2014
RS Wägetechnik
  • Developed a back-end calculating the advanced metrics over the calibration data collected from various high-precision measurement devices.
  • Built a login system and infrastructure with access control and user management.
  • Designed and implemented a front-end desktop application interface to input and manage calibration data.
Technologies: Git, Visual Studio, Windows Presentation Foundation (WPF), .NET

Contact Tracing Gateway System for Germany

I helped develop the security model and implementation of IRIS connect, a nationwide service in Germany that helps local health departments collect contact tracing information from the various app providers. It will be used in the majority of Germany's health departments.

Bsc Thesis on Fuzzing (Automated Software Testing)

In this study, I benchmark various different optimization algorithms on their fuzzing capabilities to find that constraint solving with optimization might not have been the key to Angoras performance. Nonetheless, results show promising directions for future research and will expand the performance and use cases for fuzzing in the future.

There's a blog post about it: https://andreas-zeller.blogspot.com/2019/10/when-results-are-all-that-matters-case.html


This is a very resource-friendly and feature-rich replacement for i3status; written in pure Rust. An open-source project that I've started and continue to maintain.

QuoteBot (German)

A neural network bot trained on quotes from famous people, generating new "wisdom" which self-improves through user feedback. It posts content on its own Facebook page. Currently it's only in German and is not active right now. The feedback home page also is currently not online due to the cost of operation.

Dieter Meurer Award

This is an award for achievement in the field of legal computer science, pertaining in this case to my responsible disclosure of open-access database breaches (early '15). The link refers to the paper that we published in response to the incident.

Specialized Lectures

These are some of the specialized courses that I attended in university:
- Web Security
- Cryptography
- Secure Software Engineering
- Security Testing
- Cybersecurity
- Cybersecurity Project
- Security (Advanced Lecture)
- Hacking
- Mobile Security

I'm happy to answer any further questions about the topics covered.

Industrial Software Vulnerabilities

Broadcom's Critical Systems Protection software is used around the world in industrial facilities.

During my work as a penetration tester, I've uncovered many critical software vulnerabilities like this one:

Dell Software Security Acknowledgment Program

This program was made for the vulnerabilities in the Dell update system which I discovered and helped to fix.
2014 - 2018

Bachelor's Degree in Cybersecurity

Saarland University - Saarbrücken, Germany


Microsoft Visual Studio, PyCharm, Git, Visual Studio, IntelliJ IDEA, CLion


Linux, Android


C#, Python, C++, Go, SQL, Rust, C, Java


Concurrent Programming, Penetration Testing, Agile, Software Testing


MongoDB, PostgreSQL


.NET, Windows Presentation Foundation (WPF), Django, Flask, ASP.NET, .NET Core

Industry Expertise



Cryptography, Security Testing, Security, Incident Response, IoT Security, Web App Security

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