A short summary of clefru

Free Software

portait picture of meYou might have landed on my page because you have seen software written by me. I admit it. I am a strong free software supporter. I have no underlying theory or ideology, why I do so. I just like to take things apart, especially when they don't work as intended. Free software allows me to do so. Sending a quick patch to the maintainer for a fix is something gratifying, because you know that somebody else will profit from your work.

While I have never been payed for any of my free software work, I have always been fortunate enough that I can cross-finance my passion for software with other activities. The result is that Google finds my name about twenty thousand times, mostly in free software related content.


I have two very distinct and different professional periods in my life. The first starts of as a consultant of a small family owned consulting company in Vienna and sometime in 2008, I became its general manager. The company focused on project work, ranging from warehouse logistics to data analysis of goods movements to production cost planning. While running a company and acquiring projects was sometimes stressful, the role allowed me to travel extensively, and during project-free time, I could enjoy a great work-life balance.

The second half and larger part, I spend working for Google Switzerland. In 2011, I joined as Site Reliability Engineer and found myself promoted to Senior Software Engineer at the end of my time there. I was close to payments production systems, fraud detection in particular, followed by big data products. I was the production tech-lead for Dataproc. I left Google in April 2017 to become an entrepreneur.


TU LogoAs Master of Science, I am an alumuns of the Vienna Univeristy of Technology. My major was Computer Science & Economics. My diploma thesis was nominated best of Summer 2005 by the faculty of Computer Science. It is concerned with hard disk encryption and builds the theoretical foundation of LUKS. Google Scholar lists my thesis as the most relevant paper written when searching for "hard disk encryption".


 lock I consider LUKS to be my biggest contribution to the free software world. LUKS is a hard disk encryption standard for Linux. With the first proof-of-concept published in 2004, LUKS quickly gained adoption among all Linux distributions. As of today (2017), the Debian and Ubuntu popularity contest report a 2.5%-5% regular usage of LUKS among their users. I expect this numbers to be similar across all Linux distributions. With around 100 Million Linux users world-wide, this would put the LUKS installation base somewhere between 2.5 Million and 5 Million.

ESSIV is another contribution. It is a simple hardening scheme to obfuscate the IV in CBC. ESSIV is used by all Android devices reaching potentially many millions of people.

Programming Languages

While I am not dogmatic about programming languages and while I am happy to pick up a new one over a rainy weekend, my favorite is still Lisp. S-Expression are simple and beautiful, easy to parse and surprisingly flexible. With Liskell, I created an S-Expression based representation of Haskell, which was surprisingly natural to use. I hold the believe that this can be done to any language, and put all languages onto the same parser.


Go Board with stonesI enjoyed playing Go also known as the Game of Baduk (13-14 Kyu European Rating). I run, swim, cycle, and -- as my nationality requires -- ski.