Decoding SSTV and Audio Signals | Hardwa ...

Decoding SSTV and Audio Signals | Hardware Hacking P4 | HackTheBox Signals

Feb 25, 2024

We covered the fourth part of hardware hacking series where we used HackTheBox Signals for demonstration purposes. We had an audio file with .wav format which we discovered it contained SSTV encoded signals. We used special software named RX-SSTV decoder along with a virtual cable software (VB-Audio) to connect the audio file as input to the SSTV decoder and we were able to extract the underlying image file that contained the challenge flag.

Full Video Walkthrough can be found here

Challenge Description

Some amateur radio hackers captured a strange signal from space. A first analysis indicates similarities with signals transmitted by the ISS. Can you decode the signal and get the information?

Video Transcript

It's another Hardware hacking challenge. It's an audio file or WAV file waveform file.
So you might be tempted. Let's go ahead and open this  using any media player such as VLC but it does play nothing so this got me thinking that this must be an encoded message.
Image form or text form transmitted through this audio file and it is encoded. If you go back to the description, I have actually struggled with this a while. If I use the word radio signals ISS The first thing that popped up in Google is this article. So if you click on that article You can see Here an article about the ISS which is International Space signal among them is ISS slow scan TV
So here they explain about what is called the SSTV or slow scan television.

So eventually we now know that this file holds SSTV signals and definitely signals hold some content within it we have to learn how to decode that content. So the first step is to install the relevant programs. The first program
We have to install is It is the RX-SSTV which  decodes SSTV signals  Okay, so that's the program interface and in there , we can specify the input of the program from the SSTV engine option in the menu and from here in the sound card section will be able to specify the input. Okay, so we have some how to let the program  takes the the audio file as an input without using the import option because there is no import option here. To be able to do that. You have to use Virtual cables.

We can open the file now in VLC media player, choose 'Audio' in the menu and select the virtual cable. This will feed the audio file while it's playing to the RX-SSTV program which will eventually read in the audio and decode it into the actual content which is an image file with the flag.

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