HACKVent 2014 - Day 19 writeup
I’ve sign up for the Hackvent event made by the guys from www.hacking-lab.com, which is a advent-like hacking competition. Every day there is a new challenge posted at midnight which has a to solved at best in the same day, the challenge becoming increasingly more difficult every week completed. The aim in every puzzle is to find either a qr-encoded x-mas ball with lead to the validation code, or a secret human-readable string which gives you the former ball when feeding into a validator (the “Ball-O-Matic”).
YYYYYYYYY Part :
For the Day 19 Hackvent challenge, we were given the following instructions :
Again, there is no exploration part in this challenge : the image has a code hidden somewhere in it and we have to use the logical equation written to decode it.
For that matter, I’ve converted the steg bmp image into a serie of hex numbers and striped the header. Then I used the following routine :
This is the result :
The qr code is not readable yet. We have to clean it up a little. I used a median filter with a 5px radius on it :
(imagemagick's) convert.exe img.bmp -median 5 img_med5.bmp