# Not Slick
## Challenge:
My friend always messes with PNGs.... what did he do this time?
## Solution:
All we have a is [a broken PNG](notslick.png).
Running `file` doesn't give us much:
```bash$ file notslick.pngnotslick.png: data```
Which isn't surprising, the [file signature](https://en.wikipedia.org/wiki/List_of_file_signatures) doesn't seem to match anything:
```bash$ xxd notslick.png | head00000000: 8260 42ae 444e 4549 0000 0000 2b2c edb5  .`B.DNEI....+,.....```
But if we run a Google search for `B.DNEI`, we find some other CTF challenges that indicate that this is actually a reversed PNG.
Sure enough, we can see the telltale indicator of a PNG at the end of the file:
```bash$ xxd notslick.png | tail...00018c80: 8007 0000 5244 4849 0d00 0000 0a1a 0a0d  ....RDHI........00018c90: 474e 5089                                GNP.```
Repurposing a script borrowed from [this CTF write-up](https://ctftime.org/writeup/18056), we can repair our PNG:

That gives us our flag: `UMDCTF-{abs01ute1y_r3v3r53d}`.