No need for Brutus

Challenge Statement

Author:@aenygma

A simple message for you to decipher:

squiqhyiiycfbudeduutvehrhkjki

Submit the original plaintext hashed with MD5, wrapped between the usual flag format: flag{}

Solution

The title includes Brutus who is known for betraying Julius Caesar. Caesar happen to be named after a cipher he created, The Caesar cipher, also known as ROT cipher.

This suggests that the cipher provided might be a ROT cipher for which we don’t know the key for.

Using Cyberchef we can use the recipe ROT13 Brute Force to list all possible plaintext for the cipher.

We find a plain text with key value of 10. Since the challenge requires us to use the MD5Sum of this plaintext we can calculate it using:

echo -n "caesarissimplenoneedforbrutus" | md5sum

Covering the obtained hash with flag format yields the flag