[Nullcon HackIM 2014] Misc 3 WriteUp

[Note] Credit goes to Noel94 from the club.

Points: 300
Description: What you hear is not what you always hear. Channel your energy in finding the unknown.
File: Level3.mp3

When I first played the song Level3.mp3, I immediately recognized it as a backwards or reversed song. How does one find out if a song is reversed? It depends on the experience or, in my case, the instinct of the listener.

When played, a reversed song does not sound like an ordinary song. In each part, it becomes a sound that begins quietly and ends with a powerful attack. If I were to describe how each part sounds like, I would say it sounds like something comes close from far and suddenly disappears. This is how I discovered that Level3.mp3 is a reversed song.

To put it back to the state it used to be, an audio editing program is needed. I used Audacity in this case.

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After using the reverse effect, Level3.mp3 was restored to its normal state, as seen below.

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I played the normalized Level3.mp3, and thought the answer had come out. The song sounded like an Indian song at the beginning, could the answer be India or Indian? None of them worked. There was more.

If you listen to the song using headphones or earphones, you will easily find out that the song comes out only from the left side, while the right side remains silent. But check out the image below.

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This is the track of Level3.mp3 in waveform, as shown in Audacity. The upper wave represents the left track, while the wave below represents the right track. This means that Level3.mp3 is a stereo track, in which different sounds can be stored in each side of the track. This leads to the possibility of hiding secret message in one of the tracks. From the image, everything seems normal in the left track, as listened by our left ear. However it is abnormal that the right track appears as a straight line instead of a wave shape.

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If we zoom in and look closely at the right track, it is not a straight line, but a wave formed by big and small dots. Notice the word dots. If I say big and small dots, nothing will come into your mind. How about long and short dots?

In case you had not realized, there is a way to encode text information called Morse code, which is well-known worldwide by now. It basically uses long and short tones, lights, or clicks to represent Latin alphabets, Arabic numerals and punctuation and procedural signals. For example, the famous tone bibibi-beebee- bibibi that is heard when we receive SMS, literally stands for the word SMS.

Seeing the long and short dots in the right track reminded me of Morse code. By using the chart found on the internet, we can already solve the question. Just refer to the alphabet or punctuation each set of dots stands for, and we can find out the answer in no time.

This is an alternate option for those who cannot figure out the actual dots in Audacity. Convert the normalized Level3.mp3 into a Wave File (*.wav) and analyze it using an application called Spectrogram, and we can see the dots clearly in the right side track, as shown in the image below.

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Though this is not necessary since we can already figure the dots out in Audacity.

After decoding, the Morse code hidden in the right track represents the following sentence:

ilovegoa!nullcon2014isawesome!!

And that is the actual answer for this question. Note that caps lock and words splitting is not needed, since the answer would turn out to be wrong.

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