> For the complete documentation index, see [llms.txt](https://simon-6.gitbook.io/simoncyber/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://simon-6.gitbook.io/simoncyber/ctf-writeups/picoctf-2025/cryptography/guess-my-cheese-medium.md).

# Guess My Cheese (Medium)

### The Challenge 

<figure><img src="/files/AUTct4ZLfXir27k96zUm" alt=""><figcaption></figcaption></figure>

<figure><img src="/files/PumSfnrSh16RthkWUCBt" alt=""><figcaption></figcaption></figure>

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### Solving It

This challenge isn't really helpful in the way it doesn't tell us what cipher it uses. It's not encoding, hashing, or some algorithm obviously, so we pretty much need to just trail and error every cipher we have. Personally, this challenge isn't really good, but let's just do it anyways.&#x20;

<figure><img src="/files/7G9Q7ZsOlOXG6m7Ogbqu" alt=""><figcaption></figcaption></figure>

The first thing I did was to pick a cipher that best matched the layout of the encrypted message. The one I saw matched the most was the Affinity Cipher. Hence I used a Affine Cipher.

For Affine Cipher, you need to have two key values, a and b. It's basically like an advanced Ceaser Cipher. However, this is easily cracked since its max values are 26, the amount of letters in the alaphabet. Hence, we could use some website to brute force it.&#x20;

<figure><img src="/files/ZqgdN0S36OVO0jgkKjEC" alt=""><figcaption></figcaption></figure>

And here, we easily get the answer at the top, which ended up being TRONCHONNIS. Weird.&#x20;