Going Old School

Challenge:

Unable to use their RSA encryption program, luciafer resorts to using old school techniques to send a message out to the team. Can you decipher the code and find the flag?

Submit the flag as flag{flag text}

env.deadface.io

Solution:

The provided image contains what appears to be a tabula recta for the Vigenère cipher, however the rows and columns have been reversed to Z-A as opposed to A-Z. Additionally, there is some ciphertext below the table and at the bottom of the image are a series of visual representations of Braille characters.

We started by translating the Braille based on an online table which translated to:

PORT #47980


The challenge description included a hostname so we tried connecting to the host on the port we just deciphered and received a single word as a response:

$ nc env.deadface.io 47980
GOBLINS

Next we decrypted the ciphertext DT UFAWDL IQYXFKVL manually by using the provided tabula recta and GOBLINS as the key (it wasn't until afterwards that we realized the Vigenere solver on dcode.fr has the option to provide a custom alphabet…)

The accepted flag was: flag{WE STRIKE TOMORROW}