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Arjen Wiersma

My name is Arjen. I am a Cyber Security Consultant for Scyon. I help organisations with their Application Security, Offensive Security and (Cyber) Business needs. Roles that I like to fulfill: Engineer Manager, Senior Developer (Java), Architect, (C)ISO.

I have been in the software and security industry for almost 30 years and have worked in:

  • Internet providers (Chello / UPC, Tiscali - NL): Java
  • Startups (Personify - USA, eBuddy - NL): Java, Big Data
  • Healthcare and FinTech (Infomedics - NL): Java and dotNet - Managed the IT and Development teams
  • EduTech (NOVI - NL): Managed the development team building in Serverless, Javascript
  • Education (Hogeschool van Amsterdan / NOVI - NL): teaching software security and software engineering courses
  • Cyber Security (Independent): helping organisations with their security posture

I am a member of:

  • NLJUG: The dutch Java user group
  • VERSEN: The dutch association of software engineers
  • OWASP: The OWASP Netherlands chapter

In 2024 I completed my Masters’ Degree. My research topic was BiDE, a language and architecture for the creation of bidirectional diagrammatic editors. In essence a way to modify program text using diagrams and text at the same time, allowing stakeholders of different backgrounds to work on the same system at the same time. I worked on this thesis with Bastiaan Heeren (Open Universiteit) and Jurgen Vinju (Centrum Wiskunde en Informatica).

In my spare time I love to explore the cutting edge of software engineering, exploring new languages such as Rust, Clojure and Golang in combination with Large Language Models and their novel applications.

I toot on the fediverse as @credmp@fosstodon.org and on @arjenwiersma.nl on Blue Sky.

Find my longer form writings in the Writing Category.

The views on this site are my own.

Recent posts

  1. Advent of Code 2025 Day 1

    Each year I like to participate in the Advent of Code. This year there will be 12 puzzles to solve due to Eric taking care of himself, good on you!

    My language this year is Clojure . My solution is quite simple and straightforward. I read the data using split-instructions, transforming the L into a subtraction. For part 1 it is enough to then take the reductions and then filter out all the times we land on the digit 0.

  2. Learning to Type

    I was under the impression that I was a good typist, but getting an ergonomic keyboard taught me otherwise.

    I have long been fascinated by the world of keyboards. I have several mechanical keyboards, most from Ducky. They are wonderful, but they all have in common that they are traditional keyboards. This means that your hands are close together on the keyboard, closing your chest and forcing your hands in an awkward position. We all have become very used to this position, as this is the way typewriters taught us all how to type.

  3. Scratching an Itch

    Yesterday I had a technological itch. I was configuring a package in Emacs and had to search for a variable name, the completion system mixed variables and functions together and it was a bit of a chore. Then I thought “how hard can it be to just create a utility function to list all customizable variables?”. An (sidenote: And then I spent quite some time tinkering of course :)) later my new package, upiv, was born. You can get it from my forgejo instance.

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