PicoCTF Writeup – la cifra de
# Information:
CTF Name: PicoCTF
CTF Challenge: la cifra de
Challenge Category: Cryptography
Challenge Points: 200
PicoCTF 2019.
# Challenge Description:
I found this cipher in an old book. Can you figure out what it says? Connect with nc jupiter.challenges.picoctf.org 5726.
Hint: There are tools that make this easy. Perhaps looking at history will help
# Writeup
In this challenge we are given a netcat host and address, the entire command in fact. I went to my Linux terminal and copy paste it, this was the output:
By looking at this it is easy to understand that we are in the presence of some kind of substitution cipher. Knowing this and by reading both the challenge title and the hint, I thought that maybe it is an old cipher from a French man. I then started thinking about French named ciphers and Vigenère cipher came to mind!
I decided to read a little about it, and as I thought it is a substitution cipher and Vigenère was French. I search online for a tool that cracked this type of cipher and I came across this one.
I then decided to copy the first sentence of the encrypted message and paste it on the tool to see if it was able to crack it. This was the result:
And the flag is:
Thank you very much for reading!
Cheers,
MRegra
