Description:

Lost Friends | Stego 300

Moana and her friends were out on a sea voyage, spending their summer joyously.
Unfortnately, they came across Charybdis, the sea monster. Charybdis, furious over having
unknown visitors, wreaked havoc on their ship. The ship was lost.

Luckily, Moana survived, and she was swept to a nearby island. But, since then, she has not seen her
friends. Moana has come to you for help. She believes that her friends are still alive, and that you are the
only one who can help her find them

lost_friends.png

Moana has lost her friends and we need to help her find them. We are given with an image which is absolutely blank. I opened it in Photoshop and saw that it’s completely transparent. So I grabbed python and Pillow and canceled the alpha channel (which is responsible for transparency).

from PIL import Image
# convert from RGBA to RGB will cancel transparency
Image.open('lost_friends.png').convert('RGB').save('output.png')

I got this image:

Wooho, Chipmunks! It seems like every chipmunk is on another channel, lets split the channels:

import cv2
import numpy as n
img = cv2.imread('lost_friends.png',cv2.IMREAD_UNCHANGED)
b,g,r = cv2.split(img)
cv2.imwrite('b.png',b)
cv2.imwrite('g.png',g)
cv2.imwrite('r.png',r)

Now we have three images of chipmunks:

I played with them, trying to find the flag but found nothing. So I got back to the original image and opened it with Hex Editor. At the bottom of the file I found this hint: “Psssst, Director, maybe ??”. So the flag is probably the name of the director of chipmunks. According to Wikipedia, Chipmunks has 4 movies, I tried to submit with each director and found that the director of the third movie is the flag.

The flag was praganctf{MikeMitchell}