Hackvent 2019: Day 7

Challenge

HV19.07 Santa Rider

Santa is prototyping a new gadget for his sledge. Unfortunately it still has some glitches, but look for yourself.

Resources:

For easy download, get it here: HV19-Day7-SantaRider.zip

Solution

We watch the provided video and notice that about half way through the LEDs light up in an interesting order. There are 8 total LEDs and multiple LEDs light up at once so we think that this may be hidden binary messages that decode to ASCII. As the video moves very fast its necessary to inspect each frame individually. We can do this by extracting each frame using a tool like FFmpeg but in this case it was faster to simply use a video editor like MPC-HC which allows you to navigate the video frame by frame.

It is very cool to note that because the video is stationary and position of LEDs do not move, one could use a computer vision library like OpenCV to extract the hidden binary.

We get the following binary:

01001000
01010110
00110001
00111001
01111011
00110001
01101101
01011111
01100001
01101100
01110011
00110000
01011111
01110111
00110000
01110010
01101011
00110001
01101110
01100111
01011111
00110000
01101110
01011111
01100001
01011111
01110010
00110011
01101101
00110000
01110100
00110011
01011111
01100011
00110000
01101110
01110100
01110010
00110000
01101100
01111101

We convert this binary to ASCII and get our final flag!

Flag:

HV19{1m_als0_w0rk1ng_0n_a_r3m0t3_c0ntr0l}

Bonus

This challenge also contained the solution to HV19.H2 Hidden Two