# SETI

Misc

At least 14 solves, 150 pts

### Description
Our satellite dish recieved this transmission from Alpha Centuri. Can you decode it?

[File](https://github.com/StrixGoldhorn/CTF-Writeups/blob/main/Tenable2021/Assets/tx.wav)

### Solution
Opening the file in Audacity and switching to spectrogram, we can see what looks like data being transmitted

Using the `file` command in UNIX, we get this:

````
$ file tx.wav
tx.wav: RIFF (little-endian) data, WAVE audio, Microsoft PCM, 16 bit, mono 48000 Hz
````

Now, time for some background knowledge. Satellites sent to explore the wonders of space usually use a lower baud rate.

How is this related to the challenge?

We use minimodem to read the data, but to do so, we first need to change the file extension from `.wav` to `.s16` (as it is 16 bit)

Then, we start from the lower baud rates, RTTY and TDD at 45.45 bps. This unfortunately yields no result.

Yet, we should always persevere onwards. Using Bell103 at 300 bps, the flag magically appears.

````
$ minimodem -f tx.s16 300
### CARRIER 300 @ 1250.0 Hz ###
flag{our_technology_is_immaculate}

### NOCARRIER ndata=35 confidence=2.414 ampl=0.992 bps=300.00 (rate perfect) ###
````
> flag{our_technology_is_immaculate}

Original writeup (https://github.com/StrixGoldhorn/CTF-Writeups/blob/main/Tenable2021/SETI.md).