# Misc
# YUSA’s little secret
The clue was roughly: “LSB, but not quite LSB. Everyone knows there’s more than RGB...” Opening the image in StegSolve, I could already make out the flag in two channels, but there was far too much noise to read it clearly.
That clue sent me looking at other colour spaces. Hardcore Watermark 01, a Misc challenge from ByteCTF 2020, gave me a useful lead.
A pixel can be represented by three channels. Red, green and blue are familiar examples; the channels used in this challenge are Y, Cr and Cb.
I used cv2.cvtColor(img, cv2.COLOR_BGR2YCrCb) to convert the image from BGR to YCrCb, then saved the result.
from cv2 import cv2 | |
img = cv2.imread('Yusa.png') | |
cv_color = cv2.cvtColor(img, cv2.COLOR_BGR2YCrCb) | |
cv2.imwrite('img.png', cv_color) |
Then I reopened the saved image in StegSolve and inspected its channels.
