After unzipping the given zip file with `unzip challenge.zip`, we can see two images.
* ciphered_message.png* secret.png
I checked the images with [strings](https://linux.die.net/man/1/strings), [exiftool](https://github.com/exiftool/exiftool) and [hexdump](https://man7.org/linux/man-pages/man1/hexdump.1.html) tools.But, there's nothing interesting in them.
Then, I read the **description** carefully again.
"A fun **VISUAL CRYPTOGRAPHY** tool will amaze your kids!"
I thought `visual cryptography` must be a thing.So, I searched `visual cryptography` online and found this [github repo](https://github.com/ageron/visual_crypto).
![](https://raw.githubusercontent.com/MikelAcker/CTF_WRITEUPS_2021/main/TMUCTF_2021_Writeup/Welcome/Warmup/imgs/info1.png)
### In Usage Section
![](https://raw.githubusercontent.com/MikelAcker/CTF_WRITEUPS_2021/main/TMUCTF_2021_Writeup/Welcome/Warmup/imgs/info2.png)
So, we have to *overlay* these two images and adjust the *transparency* to get the *original* image back.
I used this [online overlay tool](https://www.imgonline.com.ua/eng/impose-picture-on-another-picture.php) to do that.I didn't change anything in *setting*.
![](https://raw.githubusercontent.com/MikelAcker/CTF_WRITEUPS_2021/main/TMUCTF_2021_Writeup/Welcome/Warmup/imgs/info3.png)
Then, I clicked `OK` button.
After a few seconds, the process is completed and I opened the *processed* image.
At first, I couldn't see anything.
But then, I zoomed in the image and found the flag!
![](https://raw.githubusercontent.com/MikelAcker/CTF_WRITEUPS_2021/main/TMUCTF_2021_Writeup/Welcome/Warmup/imgs/info4.png)
*flag*: `TMUCTF{W3_h0p3_y0u_3nj0y_7h15_c0mp371710n_4nd_7h4nk_y0u!}`