HackEurope 2026: Application Challenge CTF Writeup

The HackEurope 2026 hackathon application includes an optional hidden puzzle, a multi-stage CTF challenge spanning two websites, an SSH server, and a cryptography problem.

This repo documents how I found and solved it.

The Challenge

"Solve the hidden puzzle to find the code. I'd start by looking around this website. This is not mandatory."

No instructions. No links. Just a text field and a hint to start looking.

What It Involved

1. Web Reconnaissance: Finding hidden clues in page source, browser console, and JavaScript bundles across hackeurope.com and registration.hackeurope.eu
2. SSH Access: Piecing together a username, IP, and password from the clues to access a remote server
3. Cryptography: Breaking a weakened Diffie-Hellman key exchange using Pohlig-Hellman, factoring, and XOR decryption

Solution

The full step-by-step writeup with reasoning and theory explanations:

HackEurope_CTF_Writeup.md