HACKvent 2019: Day 1

02 Dec 2019
CTF: Hackvent 2019
Link to challenge:
Date Completed: 2 December 2019



HV19.01 censored


The hint indicates that we should have a clearer smaller image available to us.
At first we attempt to shrink the image, resharpen and enlarge but there is too much degradation for that to work. We also open the image in GIMP and mess with levels/contrast with no luck.

Finally, we use binwalk on the image to find hidden binaries and find:

We extract the second JPEG image in this file which gives us a smaller preview thumbnail but with a crisp QR code!

This image is good enough to scan and gives us our flag!

Flag:  HV19{just-4-PREview!}

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Advent Of Code: Day 1

02 Dec 2015
CTF: Advent Of Code
Link to challenge:
Date Completed: 01/12/2015

The Challenge



Before part 2 of the problem was revealed I decided to tackle the problem using the command line. I cam up with the following command:

We echo the input and remove the ) symbol which leaves only ( and we use wc to count the number of  ( symbols which tells us how many times we went to a higher floor. We then subtract his number from the number of times we went to a lower floor (using bash arithmetic) which gives us our answer.

Part 2 of the problem would be annoying to do on the command line so I decided to write a quick python script to solve it. The solution also solves the first part of the problem (lol).


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