vishwaCTF 2021: Sherlock | szymanski.ninja

Sherlock

Category: Forensics

467 points

Sherlock found a green envelope on its door step and this image.

file: decode.jpg

Solution

I’ve evaluated the image and found something interesting on the left edge of it.

Simple python script reveals the secret.

from PIL import Image

im = Image.open('/home/luc/Pobrane/decode.png')

binary_flag = ''
for i in range(2):
    for j in range(im.size[1]):
        if im.getpixel((i, j))[1] == 255:
            binary_flag += '1'
        else:
            binary_flag += '0'

print(''.join([chr(int(binary_flag[i:i+8], 2)) for i in range(0, len(binary_flag), 8)]))

vishwaCTF{@w3s0Me_sh3Rl0cK_H0m3s}ÿÿÿÿÿÿÿÿÿÿ

Flag

vishwaCTF{@w3s0Me_sh3Rl0cK_H0m3s}