Challenge 46 — Hidden Message Part 2

TraceLabs CTF — Audio Forensics & Morse Decoding

The challenge

Category: Medium File: Audio WAV Objective: Find the hidden message

Step 1 — Transcript

First pass: transcribed the audio with ElevenLabs. The spoken text was:

“Thanks to innovation and faith, we can connect across distances, stop elevating mankind to a new and different levels for a new technology, new era. What hath God wrought?”

The last sentence is not random. “What hath God wrought?” is the first official message ever transmitted by Samuel Morse via telegraph, on May 24, 1844. Combined with “connect across distances” and “new era” — the text was a signpost pointing directly at Morse code.

Step 2 — Spectrogram analysis

Opened the file in iZotope RX and examined the spectrogram. The audio had a clear two-part structure.

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Isolated the Morse tail.

Step 3 — Decoding

Used a custom Python script (built for Challenge 45 and reused here) based on Hilbert transform envelope detection:

1. Extract signal envelope via hilbert()
2. Smooth with 5ms moving average
3. Threshold at 30% of peak → binary ON/OFF sequence
4. Run-length encode → classify dots/dashes by duration
5. Translate via Morse table → ASCII

python3 decode_morse.py morse_tail.wav

Output:

Morse raw: - .... . / ..-. .. -. -.. . .-. / --- ..-. / -- --- .-. ... . / 
           -.-. --- -.. . / .. ... / -.-- --- ..- .-. / ..-. .-.. .- --. 
Decoded: THE FINDER OF MORSE CODE IS YOUR FLAG

Verified with a second run at 20% threshold — identical result, high confidence.

The clue & flag

The clue: THE FINDER OF MORSE CODE IS YOUR FLAG
Flag: Samuel F.B. Morse

Key lessons

The transcript was the real clue. “What hath God wrought?” is not decoration — it’s a direct historical reference to Morse code’s first transmission. Reading the audio content carefully pointed to the attack vector before opening a single tool.

Reuse what works. The decoder script built for Challenge 45 solved Challenge 46 without modification. Document and keep your tools.

The spectrogram before everything else. Visual inspection of the audio separated voice from tone in seconds, making the extraction trivial. Always look before you listen.

The hidden message was hidden in plain sight — encoded in the technology its own transcript was describing.