collision

Collision

Level - Hard

Description:

Can you make 2 PNGs with the same MD5 hash, but different pre-defined strings inside of it? Go ahead!

`nc byuctf.xyz 40016`

[verify.py]

Writeup

I used the PNG collision script made by corkami. pic1.png and pic2.png are the two base "PNGs" that I used. To generate collision1.png and collision2.png (that meet the requirements), I just ran png.py pic1.png pic2.png.

Flag - byuctf{c0ll1s10n5_4r3_c00l10}

Hosting

This challenge should be a Docker container that runs python3 verify.py on port 40016. All the proper files are included in here. The command to build the docker container is (when located inside of this directory):

sudo docker build -t collision .
sudo docker network create -d bridge collision

The command to start the challenge is:

sudo docker run -p 40016:40000 --detach --name collision --network collision collision:latest

The command to stop the challenge (since CTRL+C won't work) is:

sudo docker stop collision