In this stego challenge we are given a password protected zip called turtles128.zip. After bruteforcing it we observe that there are 128 nested zips protected with “0” or “1” as their password. We suspect that the flag is hidden in the data obtained from the binary passwords.
Inside the last zip we find the key.png image that contains a password in hexadecimal. Observing the name of the challenge (A3S), the name of the zip (turtles128), the length of the key and the number of bits obtained when decrypting the zips, we deduce that the flag is encrypted with AES128, using the key in key.png.
Data: 3DC906F6928EE882CCB1B8BDD14AA24C
Key: ed570e22d458e25734fc08d849961da9
We can obtain the flag with AES decryption using the image key and the bits obtained in the zip decryption process.
Flag: flag{steg0_a3s}