Rating:
# SECCON CTF Quals - 2019
## Misc / 279 - Sandstorm
> I've received a letter... Uh, Mr. Smith?
> 
### Solution
By [@afcidk](https://github.com/afcidk)
From the provided image, we can guess that this challenge is related to Adam7, which is an interlacing scheme for PNG images. Adam7 has seven passes, so I decide to generate those seven subimages first, and see if there is any clues.
I wrote a simple script to transform the original [sandstorm.png](./imgs/sandstorm.png) to seven images using Adam7 algorithm.
Level 1:
Level 2:
Level 3:
Level 4:
Level 5:
Level 6:
Level 7:
The flag is encoded to QR code in Level-1 subimage, `SECCON{p0nlMpzlCQ5AHol6}`.
### Reference
* [Adam7 algorithm](https://en.wikipedia.org/wiki/Adam7_algorithm)
