HACKvent 2020 - Day 5

01-01-2021 - 2 minutes, 11 seconds - CTF

Challenge - Image DNA

Santa has thousands of Christmas balls in stock. They all look the same, but he can still tell them apart. Can you see the difference?

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HACKvent 2020 - Day 4

01-01-2021 - 1 minute, 25 seconds - CTF

Challenge - HV20.04 Br❤️celet

Santa was given a nice bracelet by one of his elves. Little does he know that the secret admirer has hidden a message in the pattern of the bracelet…

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HACKvent 2020 - Day 3

01-01-2021 - 2 minutes, 1 second - CTF

Challenge - Packed gifts

One of the elves has unfortunately added a password to the last presents delivery and we cannot open it. The elf has taken a few days off after all the stress of the last weeks and is not available. Can you open the package for us?

We found the following packages:

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HACKvent 2020 - Day 2

01-01-2021 - 1 minute, 16 seconds - CTF

Challenge - Chinese Animals

The challenge description of day 2 read:

I've received this note from a friend, who is a Chinese CTF player:


Unfortunately, Google Translate wasn’t of much help. I suspect the data has somehow been messed up while transmitting...

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HACKvent 2020 – Day 1

01-01-2021 - 0 minutes, 36 seconds - CTF

Happy HACKvent 2020

Welcome to this year’s HACKvent. Attached you can find the “Official” invitation to the HackVent. One of my very young Cyber Elves cut some parts of the card with his alpha scissors.

Have a great HACKvent,

– Santa

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HACKvent 2020 - Day -1

01-01-2021 - 1 minute, 46 seconds - CTF

This is the teaser challenge, released a day before the start of this capture the flag event. We were presented the following text.

On the third day of christmas my true love sent to me…

three caesar salads,
two to (the) six basic arguments,
one quick response.

Sbopb 3 alkb! Lcc tfqe vlr! Db...

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Ray-Sphere Intersection - From Math to Code

08-10-2020 - 6 minutes, 20 seconds - Computer Graphics

In this article I derive a ray-sphere intersection algorithm from it's math. While certain knowledge in mathematics and programming will be assumed, I am trying to show all the steps of the process.

Ray-sphere intersection is used to determine wether and where a ray hits a sphere. This is useful in selecting 3D objects with the cursor (well, spheres in this case), calculating bullet hits in games, etc., but you knew that. Why else would you look up such a specific topic?

So let's start with what we have: a sphere (your object, a hitbox, ...) and a ray (a bullet, your cursor, ...). What we we'd like to know is, if they intersect and what the intersection point(s) are, if any.

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Use Unsupported Hotkeys in KeePass

08-03-2020 - 1 minute, 38 seconds - IT

For years I have used the "Open Calculator"-button on my keyboard as a hotkey to open KeePass. When I set up my new laptop, I wanted to configure KeePass to use my hotkey again – but it didn't work anymore.

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Fixing the ISOs Work

04-07-2020 - 1 minute, 49 seconds - Rant ASN.1

Recently I had to implement encoder/decoders for some ISO standardized data structures in the area of intelligent transport systems. It's always nice having standards. Work went well until I encountered ISO 14823:2017. Up to this, for some strange reason, I considered ISO standards as infallible a...

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A Simple ReverseProxy Using PHP

03-29-2020 - 1 minute, 59 seconds - Coding PHP

In the course of the last week i moved some websites from my self managed VPS to an designated webhoster. Once moved, i encountered the problem that i could not use ngnix's proxy_pass feature. So i wrote myself a little ReverseProxy using PHP.

I wanted to move the websites from the VPS to an Web...

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