CTFs

Crypto 100

First we have a pdf file

Obviously this pdf file is hiding something. Which can be unveiled by changing the file extension

First I tried images, then I did a strings in linux on the file to get this

There is a msg.txt file hidden in the pdf. At first I was trying to find tools to extract this data at the end of the file. But the point of this challenge is to extract the file by chaning the file type. What file type is capable of hiding/storing files? — A .zip file

There is the text file. But the challenge isn’t over Contents of the text file:

⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⡀⠴⠤⠤⠴⠄⡄⡀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⣠⠄⠒⠉⠀⠀⠀⠀⠀⠀⠀⠀⠁⠃⠆⡄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⢀⡜⠁⠀⠀⠀⢠⡄⠀⣀⠀⠀⠀⠀⠀⠀⠀⠀⠑⡄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⢈⠁⠀⠀⠠⣿⠿⡟⣀⡹⠆⡿⣃⣰⣆⣤⣀⠀⠀⠹⡄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⣼⠀⠀⢀⣀⣀⣀⣀⡈⠁⠙⠁⠘⠃⠡⠽⡵⢚⠱⠂⠛⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠈⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⡆⠀⠀⠀⠀⢐⣢⣤⣵⡄⢀⠀⢀⢈⣉⠉⠉⠒⠤⠀⠿⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠘⡇⠀⠀⠀⠀⠀⠉⠉⠁⠁⠈⠀⠸⢖⣿⣿⣷⠀⠀⢰⡆⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⢀⠃⠀⡄⠀⠈⠉⠀⠀⠀⢴⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀Kind of crazy how a zip file can also be a pdf. ⠀⠀⠀⠀⠀
⠀⠀⠀⠀⢈⣇⠀⠀⠀⠀⠀⠀⠀⢰⠉⠀⠀⠱⠀⠀⠀⠀⠀⢠⡄⠀⠀⠀⠀⠀⣀⠔⠒⢒⡩⠃⠀⠀⠀⠀⠀⠀⠀ Well good job of getting here.⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⣴⣿⣤⢀⠀⠀⠀⠀⠀⠈⠓⠒⠢⠔⠀⠀⠀⠀⠀⣶⠤⠄⠒⠒⠉⠁⠀⠀⠀⢸⡀⠀⠀⠀⠀⠀⠀⠀⠀Here is the encrypted flag below...⠀⠀⠀⠀⠀⠀⠀
⡄⠤⠒⠈⠈⣿⣿⣽⣦⠀⢀⢀⠰⢰⣀⣲⣿⡐⣤⠀⠀⢠⡾⠃⠀⠀⠀⠀⠀⠀⠀⣀⡄⣠⣵⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠘⠏⢿⣿⡁⢐⠶⠈⣰⣿⣿⣿⣿⣷⢈⣣⢰⡞⠀⠀⠀⠀⠀⠀⢀⡴⠋⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠈⢿⣿⣍⠀⠀⠸⣿⣿⣿⣿⠃⢈⣿⡎⠁⠀⠀⠀⠀⣠⠞⠉⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠈⢙⣿⣆⠀⠀⠈⠛⠛⢋⢰⡼⠁⠁⠀⠀⠀⢀⠔⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠚⣷⣧⣷⣤⡶⠎⠛⠁⠀⠀⠀⢀⡤⠊⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠁⠈⠁⠀⠀⠀⠀⠀⠠⠊⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠃⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠸⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢠⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⠃⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠘⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢀⠁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠸⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡆⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢁⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠘⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀

⢸⠉⠉⠉⠉⠉⠉⠉⠉⠉⠉⠉⠉⠉⡷⡄⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⢸⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡇⠢⣀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀
⢸⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⡇⠀⠀⠈⠑⢦⡀⠀⠀⠀⠀⠀
⢸⠀⠀⠀⠀⢀⠖⠒⠒⠒⢤⠀⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠙⢦⡀⠀⠀⠀⠀
⢸⠀⠀⣀⢤⣼⣀⡠⠤⠤⠼⠤⡄⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠙⢄⠀⠀⠀⠀
⢸⠀⠀⠑⡤⠤⡒⠒⠒⡊⠙⡏⠀⢀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠑⠢⡄⠀
⢸⠀⠀⠀⠇⠀⣀⣀⣀⣀⢀⠧⠟⠁⠀⡇⠀⠀⠀⠀...⠀is an urban legend concerning a fictitious 1981 arcade game.⠀
⢸⠀⠀⠀⠸⣀⠀⠀⠈⢉⠟⠓⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸
⢸⠀⠀⠀⠀⠈⢱⡖⠋⠁⠀⠀⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸
⢸⠀⠀⠀⠀⣠⢺⠧⢄⣀⠀⠀⣀⣀⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸
⢸⠀⠀⠀⣠⠃⢸⠀⠀⠈⠉⡽⠿⠯⡆⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸
⢸⠀⠀⣰⠁⠀⢸⠀⠀⠀⠀⠉⠉⠉⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸
⢸⠀⠀⠣⠀⠀⢸⢄⠀⠀⠀⠀⠀⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸
⢸⠀⠀⠀⠀⠀⢸⠀⢇⠀⠀⠀⠀⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸
⢸⠀⠀⠀⠀⠀⡌⠀⠈⡆⠀⠀⠀⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸
⢸⠀⠀⠀⠀⢠⠃⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⡇⠀⠀⠀⠀⠀⠀⠀⠀⠀⠀⢸
⢸⠀⠀⠀⠀⢸⠀⠀⠀⠁⠀⠀⠀⠀⠀⠀⠀⠷

A-Y 5x5
311555:3324454311

──────▄▌▐▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▀▌
───▄▄██▌█ BEEP BEEP...
▄▄▄▌▐██▌█ series of interwoven ciphers
███████▌█▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▄▌
▀(⊙)▀▀▀▀▀▀▀(⊙)(⊙)▀▀▀▀▀▀▀▀▀▀(⊙)       (⊙)

A-Z
YKT{r98c829m5j05xuf5m67mu78101vd8m77m1v0369r}

fictitious 1981 arcade game? After a google search, it’s referring to the game Polybius which is also the name for a cipher And the numbers below it are likely the encrypted text A-Y fit into the grid

And we get KEYMITRA or Key:Mitra So we know the key is MITRA

Lastly using the key MITRA I used a Vigenère cipher to unveil the flag

Flag: MCA{a98c829a5b05edf5a67eb78101ed8a77e1c0369a}