Writeup URL: [GitHub](https://infosecstreams.github.io/csaw21/mic/)# mic
Writeup by: [GoProSlowYo](https://github.com/GoProSlowYo)
Team: [OnlyFeet](https://ctftime.org/team/144644)
Writeup URL: [GitHub](https://infosecstreams.github.io/csaw21/mic/)
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```textMy Epson InkJet printer is mysteriously printing blank pages. Is it trying to tell me something?```
## Initial Research
The text seems to reference the printer "telling" us something. This 'something' is [`MIC`](https://en.wikipedia.org/wiki/Machine_Identification_Code)'s in the printer page.
> Tiny dots are embedded on printouts by modern printers. Markings like these were used to trace [NSA documents leaked to The Intercept by Reality Winner](http://www.bbc.com/future/story/20170607-why-printers-add-secret-tracking-dots).
![Yellow Dots: tiny yellow dots on the print-out representing the hidden code of an HP Color LaserJet 3700.](./HP_Color_Laserjet_3700_schutz_g.jpg) (source: https://upload.wikimedia.org/wikipedia/commons/8/8e/HP_Color_Laserjet_3700_schutz_g.jpg)
## Getting the Flag from the Printed Pages
First we need to quickly install some dependencies:
```shellgit clone https://github.com/dfd-tud/dedapushd deda && pip3 install --user deda && popdsudo apt install poppler-utils```
Then, we wrote a quick one liner to dump the flag:
```shell$ pdftoppm scan.pdf scan -png; for x in {01..34}; do echo -n $(python3 -c "print(chr($(deda_parse_print scan-$x.png | grep serial | cut -d '-' -f2 | sed 's/^0*//')))"); doneflag{watchoutforthepoisonedcoffee}```
![Solve Animation](./solve.gif)\
## Victory
Submit the flag and claim the points:
**flag{watchoutforthepoisonedcoffee}**