HACKVent 2020 – Day 4

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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…

Over the day, two sets of hints were given:

  1. No internet is required – only the bracelet (#1)
  2. The message is encoded in binary (#1)
  3. Violet color is the delimiter (#2)
  4. Colors have a fixed order (#2)
  5. Missing colors matter(#2)


We started the challenge in the afternoon, when all hint were already given.…

HACKVent 2020 – Day 3

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.…

HACKVent 2020 – Day 2

Challenge – Chinese Animals

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 it.

Sadly, I can’t ask my friend about more details.

HACKvent 2020 – Day 1

Challenge – 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


Those alpha scissors are clearly a hint.…

Alcatel HHV40 4G/LTE Linkhub Router – Do Not Buy!

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I don’t like to make such common product blog posts, I’d rather leave that to some ad-heavy tech sites or whatever but a rant might be just okay, so here we go:

If you like to have a reliable home network, buy something else.…

HACKVent 2020

HACKVent is hacking-labs advent calendar, with a hacking (or “capture the flag”) challenge a day.

The challenges in the beginning are rather easy, but get more complicated and time consuming each day.

Since the CTF-challenges are still in progress, our write-ups will only be released after HACKVent ends, so don’t expect the links to work before January 1st, possibly later.…

Ray-Sphere Intersection – From Math to Code

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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.
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Exchange 2010 Logs Eating Up Storage Space

The Microsoft Exchange Server 2010 writes all processes – before it enters them into its database – in “transaction logs”. From these logs, the entire database can therefore be reconstructed in the event of damage. But I don’t want to go into this in detail – if you are interested in this, you can read more about it here: link. The real problem is that these logs can eat a lot of memory over time. Read here how to free it.

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