Murder Write-up

Published on 20 Nov 2021
2 min read
DOMECTF2021

Story

Susan was found dead in her apartment. The investigation officer found a thumb drive from the crime scene. On examining the thumb drive, the officer found some images of food items are arranged in a particular order. This made him suspicious. “Your task is to help him decode the images.”

Solution

We have sent you a zip file that contains a set of folders of images with names ‘if_you_need_use_me’ and ‘predict_me’.

lockbox1

In the folder ‘if_you_need_use_me’, there will be 2 folders named ‘Dessert’ and ‘Soup’.

lockbox1

Each folder (DESSERT and SOUP) contains 2000 images that can be used for the training process. The ‘predict_me’ folder contains 1000 images of dessert and soups.

To get the flag, predict the images in the ‘predict_me’ folder correctly without changing the image order and feed it to the python file ‘flag.py’.

lockbox1

On giving a look at the images in the ‘predict_me’ folder, we can see the presence of two kinds of data (images of desserts and soups) forming a binary classification problem.

The sequence of dessert and soup is forming a message. Say that desserts are 1 and soups are 0.

In order to capture the flag, you have two choices:

  1. Find a training model to predict these images

  2. Train a model yourself

In order to train the models, you may search for online tutorials on binary classification.

lockbox1

After reducing each image to 0 or 1, you will get a sequence of bytes as a string by feeding the predicted bits to the python file ‘flag.py’ which will show you the flag.

Output:

murder1
Nasim Sulaiman
Written by
AI Engineer

Nasim Sulaiman is a distinguished AI Engineer with a profound understanding of the intricacies of artificial intelligence. With a rich background in the field, Nasim excels in leveraging AI to tackle complex challenges and drive innovation. His expertise extends to designing and implementing AI solutions that push the boundaries of what's possible.

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