Summary#

This challenge provides an audio recording containing Morse code beeps. The goal is to decode the audio into text.

Analysis#

We are given an audio file named morse_chal.wav:

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$ file morse_chal.wav
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morse_chal.wav: RIFF (little-endian) data, WAVE audio, Microsoft PCM, 16 bit, mono 44100 Hz

Since it’s a WAV file, the next logical step is to listen to it, and immediately, it becomes clear that the audio consists of classic Morse code beeps.

To decode the Morse from audio, we can use any online audio Morse decoder. One reliable option is: https://morsecode.world/international/decoder/audio-decoder-adaptive.html

Upload the file and wait for the decoder to process the signal.

The decoder output gives us: WH47 H47H 90D W20U9H7

Now we need to replace the spaces with underscores and wrap it with the flag format: picoCTF{WH47_H47H_90D_W20U9H7}

⚡ Raikiri

🎉 Flag pwned!

💡 TL;DR / Lesson Learned

Audio Morse can be decoded easily using online adaptive decoders.