Rating:

# Astatine {10 points}?

###### Challenge Description

Can you read the message?

5t4=2<(;4P0Q^YXDIYA21Ltn

###### Category : Steganography
###### Author : Jerin John Mathew (Shadow_Walker)
###### Team : Red Knights

![](https://img.shields.io/badge/10-Steganography-red) ![](https://img.shields.io/badge/-Cryptography-green)

So this is a Steganography challenge in which we have a **crypted text : 5t4=2<(;4P0Q^YXDIYA21Ltn**

The Challenge title gives us the name... _Astatine_

So....
time for a _chemistry class_ for CTF players... ?

_Astatine_ is basically one of the elements in the periodic table having an **atomic number 85**.
It is the rarest naturally occurring element in the Earth's crust.

_End of Class_

This is the hint required "85" and you need to find the type of encryption methods with 85 in their name...
OR a guy having good cryptographic knowledge can understand that it is **BASE 85 Encryption**

Now you just needed to take the string and submit to **Cyberchef** with base 85 recipie foe decrypting....
and VOILA...

![](Base85CyberChef.png)

# FLAG OBTAINED :--> AFFCTF{n0t_3nc0d3d} ... ?

For more information on base 85 :---> https://en.wikipedia.org/wiki/Ascii85

Original writeup (https://github.com/Red-Knights-CTF/writeups/tree/master/2020/affinity_ctf_lite/Astatine).