5 x 5 Crypto

Getting hands on Polybius Square Cipher

Challenge Category :- Cryptography

Challenge Points :- 60

So , Let’s get started with one of the medium based challenges on CTFLEARN . An awesome place for beginners to get started with CTF and its basic conceptions .

As we can clearly see some useful strings on the beginning of the challenge “Ever heard of the 5 x 5 secret message system” .

Let’s get to the search bar and try to find out something useful .

So according to the cipher analysis of Polybius Square Cipher its clear that the “SECRET MESSAGE” is ciphered using the the afforesaid cipher . So lets try deciphering it .

Using an online cipher decoder Cryptii we decoded the cipher text and found the flag .

“CTF{THUMBSUP}”

Hope you enjoyed the writeup :P