Description This challenge from the Misc category was saying: “Is it me or there is a strange guy on the discord server ?” Solution Joining the Server I went on the Discord server of the CTF, and found a guy named “Joe Dohn”. I sent him a message, and immediately he replied by inviting me to a private Discord server. Actually, Joe is not real person but a bot. This private server has 2 channels: a general channel, and one dedicated to conversation with me.

Those 2 challenges had already been flagged by a team mate when I started working on the CTF. But, during the CTF, at a time when I was getting frustrated not to flag other challenges, I decided to do them again on my own lol. Both challenges are very beginner friendly. Just Read Description This challenge is in the Reverse category, with a simple description “Find a way to break this” and an executable main is provided.

In this challenge at Insomni’hack CTF, you get an Android application (apk) to analyze. Had to look at that, obviously 😉. The challenge was solved as team work with 2 other team mates from Soudure au Beurre. Update April 20, 2024: PKCS7 and PKCS5 are basically the same. Corrected the explanation. Understanding the Android application In this challenge, you get an Android application. I decompile it to find a pretty simple application with 2 classes: MainActivity and Part1.