Timed Transmission was the first hardware challenge of the Hack The Box Cyber Apocalypse 2023 CTF event. Hello world, welcome to Haxez. In this post, I’m going to describe my experience solving the Time Transmission hardware challenge. All the challenges in this CTF have a great description following the theme of the competition. The introduction to the challenge was as follows.
“As part of your initialization sequence, your team loaded various tools into your system, but you still need to learn how to use them effectively. They have tasked you with the challenge of finding the appropriate tool to open a file containing strange serial signals. Can you rise to the challenge and find the right tool?”
Timed Transmission Files
After reading the description, we can download the challenge files which are achieved in a zip file. Extracting the zip files revealed a file named ‘Captured_Signals.sal’. There was also a ‘_MACOSX’ file which I presume contained the Mac OS equivalent files.
Our first challenge was to identify how to open these files. Performing a google search for ‘.sol’ files solved that question pretty quickly. Unfortunately, that was only the beginning of the challenge. Admittedly, I spent far longer on this challenge than I should have. Furthermore, the answer was under my nose the whole time, I just couldn’t see it.
Saleae Logic 2
The provided files could be opened with a program called Logic 2 from Saleae. Logic 2 allows the user to capture and analyse signals. Upon opening the file, the answer is right in front of you. The different message fragments make up the flag. Unfortunately, and embarrassingly, I didn’t see it. I spent hours trying to analyse the different channels with various different analyzers.
So provided you didn’t immediately zoom and mess with the signal, this should have been easy to solve. Unfortunately, I did mess with the signal and even went as far as extracting the individual channels from the file and looking through those. I wasted a lot of time.
Timed Transmission Review
I didn’t enjoy this challenge for the wrong reasons. It should have been a fun introduction to hardware hacking but I went and overcomplicated it. However, the challenge itself is fun and I like how the creators were able to make the signals spell out the flag.