Ctf
dJulkalender 2015: Writeups
The computer science chapter at my alma mater, KTH, arranges an advent calendar called "dJulkalendern". It is a CTF-like puzzle with challenges (almost) every day until christmas and also a competition. Last time it was arranged in 2013, I won the challenge but this year I had to settle for a third place.
Solving the GCHQ christmas challenge with Microsoft Z3
British intelligence agency GCHQ has released a christmas card. It contains a sudoku like puzzle where you color squares in a grid according to a set of constraints. The christmas card challenge along with a description can be found on their website. It looked like it could be solved by hand without too much effort but I figured it would be more fun to write a program to solve it for me. Recently I have been playing with Microsoft's constraint solver, Z3. I thought this would be a perfect tool to solve the challenge with.
As stated previously, the challenge consists of a grid, specifically a 25x25 grid with series of numbers written next to each column and row and with some of the cells already filled in. Below is an image of the grid. Apparently, this is famous type of puzzle called a Nonogram. I didn't know this until after I wrote this and a friend pointed it out. You know what they say, you learn something every day.
DefCamp D-CTF Qualifiers 2015: Writeups
A few weeks ago we participated in the DefCamp D-CTF qualifiers. We performed really well and ended up in fourth place, just a single point behind number three. This earned us a place in the finals in Bucharest at the DefCamp conference.
SEC-T CTF 2015: Writeups
Earlier this month I was at the SEC-T conference. In addition to listening to several awesome talks by very interesting speakers I also participated in the CTF which was held during the conference. We, HackingForSoju, chose to play individually rather than together in this CTF, which was available for remote players. We did this because it was a small competition and we thought it would be more fun to let everybody practice.
PoliCTF 2015: Writeups
This weekend we participacted in PoliCTF, a CTF arranged by Italian team Tower of Hanoi. It was a very well arranged 48 hours CTF with good variety and minimal amount of guesswork. We had five players working throughout the weekend: mxn, capsl, ZetaTwo, avlidienbrunn and hspe. We performed very well and ended up on second place. This brought us up to 12th place on the season scoreboard. In this post I will explain the challenges I solved: