[CryptoChallenge] Basic Stego


(pico) #1


Note: The image was not generated with any steganography tool.
Note2: In this case, the message can be extracted without coding.

Hint 1:GIMP is your friend
Hint 1.5:Use the Color>Components>Decompose to get the image components separated.
Hint 2:PGM format saves grey scale images as raw data
Hint 3:The image is pretty blue, isn’t it?. Take a look to the colour components

Nice weekend!


What an hard thing !
The most i can get is that i need a sort of blue filter to put on top of the image, but i just don’t how to make this :open_mouth:

(pico) #3

Then, you have to open the first Hint :slight_smile:

(oaktree) #4

I downloaded it, opened GIMP, decomposed it, took out the red and the green, and now I’m staring at a grayscale of the blue image, but I don’t know what to do next.

(pico) #5

man ppm

Check the SEE ALSO section, the format to use is listed there


Arrrrg this make me mad :stuck_out_tongue:

I can now see some letter (i’m playing with some gray levels on blue channel) but no idea how to get the perfect result :frowning:

PS: How can i hide my words in order to avoid spoil ?

(pico) #7

Use [spoiler] ... [/spoiler]


Finally Done !
Just Wow ! A great thing i learned today !

(pico) #9

Congrats!.. Next one will be more difficult


Got it finally! Any chance you could show us exactly how you created the image? I see there is a PNM filter mentioned in the message.

(pico) #11

Sure. I generate the image with a small program I wrote. I do not know if it is possible to generate the file just using a image processing tool. I will post the code later anyway a bit later today (I’m finishing something else).

(John Clarke) #12

Hi. New to site. Love the challenge. Still trying to complete it. When will you post the code?

(pico) #13

Hi @spoclate and thanks.

You can find the solution here


(system) #15

(oaktree) #16