Lake CTF 24-25 Quals

Since this was a qualifier, our goal was clear: finish high enough in the Academic division to earn a spot in Switzerland. Thankfully, we placed sixth and made it through. Seeing our name inside the qualifying range was a great way to end the event.

I solved two reversing challenges during the competition. a-smoll-rev was especially memorable because it was very much a team effort. One of my teammates made an excellent guess about the challenge’s core structure, and that insight gave us the direction we needed to finish the solve.

CyKor finished sixth in the Academic division.

Below are my write-ups for the two reversing challenges I solved during the qualifiers:

Write-ups

An Android Applekation

An Android reversing challenge involving a large native flag checker. I mapped the JNI functions and automated the repetitive parts of the analysis.

a-smoll-rev

A compact but layered reversing challenge involving comparison hooking, input-format recovery, and a Sudoku stage. A teammate’s insight into the underlying structure was the key that got us moving in the right direction.