The goal of this challenge is to successfully run (in a shell on a provided server) a setuid binary flag which asks you to repeat a number, and then (if you repeat it successfully) outputs the flag: This would be trivial but for one interesting restriction of the provided shell: the only characters you are… Continue reading 33C3 CTF – shjail

# Category: 33C3 CTF

## 33C3 CTF – babyfengshui

In this challenge, we are provided with a 32-bit ELF ('babyfengshui') and a libc file ('libc-2.19.so'). The program maintains a list of users, which consist of names and descriptions. Here is some example usage, where we add a user and then display it: As you can see, there are 4 relevant actions, so let's go… Continue reading 33C3 CTF – babyfengshui

## 33C3 CTF – Beeblebrox

This crypto challenge is a classic "fake-the-signature" crypto challenge, but with a somewhat unusual signature scheme that depends on the hardness of computing $latex n$th roots modulo a semiprime: There is a publicly known semiprime $latex N = PQ$, whose two prime factors $latex P$ and $latex Q$ are known only to the signer. There… Continue reading 33C3 CTF – Beeblebrox

## 33C3 CTF – Ichnixwisse

In this crypto challenge, we're given an implementation of a zero-knowledge proof system for 3-coloring a graph. We're also given a graph on 100 vertices with 4600 edges which is far from 3-colorable. Our goal is to fool the verifier on the server and prove to it that this graph is in fact 3-colorable (where… Continue reading 33C3 CTF – Ichnixwisse