Blinkybill

This is a writeup of the misc challenge blinkybill from the DUCTF(https://play.duc.tf/) CTF

Level: beginner, Score: 100

Premise

Hey hey it’s Blinky Bill!

Challenge files:

blinkybill.wav

Observations

When litsening to the wav file, we hear what sounds like morse code in the background.

Solution

Putting the wav file into Audacity, we dont get a lot to work with at a glance.

If we change the view it as a spectrogram though, we can see what looks like morse codes.

Decoding these into their respective letters we get the following:

Giving us a string that could be a flag but doesnt seem quite right, `SRINGBACKTHETREES.

Looking at the morse code, and the decoded message, a logical deduction would be that instead of the . . . or S that I currently have as the first character, I could change it to - . . . or B giving us a more reasonable string as the flag.

This gives us the flag we’re looking for.

DUCTF{BRINGBACKTHETREES}

Tools used:

• Audacity
• Alternatively: morsecode.world has a decoder that can be used
• the morse code alphabet