Challenge Description

Danish (original)

Naglfar er drevet i land under sommerens stråler. Naglfar hviler nu i en smuk sø. Ikke langt fra søen ligger et velkendt monument, som indeholder ældgammel kryptografi. Det er en meget velkendt mand som har skrevet denne kryptografi i tidernes morgen.

Hvad er navnet på søen, Naglfar ligger i? Hvilken moderne teknologi er forbundet med denne mand?

Du skal selv sammensætte flaget. Flagets format er således: FDCA{navn_på_sø_teknologi}

English (from chatgpt)

Naglfar has been driven ashore under the summer’s rays. Naglfar now rests in a beautiful lake. Not far from the lake lies a well-known monument that contains ancient cryptography. It is a very famous man who wrote this cryptography in the dawn of time.

What is the name of the lake where Naglfar rests? What modern technology is associated with this man?

You must assemble the flag yourself. The flag’s format is as follows: FDCA{lake_name_technology}

File

We are also given the following file:

Solution

Unzipping the file, we get an image:

$ unzip
Archive:  opgave.zip
  inflating: sommerdag.png

Reverse image searching the image gives a few possible location, but only one fit with the rest of the description: Faarup Lake (Fårup Sø), since the Jelling stones are nearby, which is connected to Harald Bluetooth (Harald Blåtand), the name sake of Bluetooth. So the flag is: FDCA{fårup_sø_bluetooth}