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Challenge 47: Hidden Message Part 3 (Hard) — Walkthrough

Alp Akciğer2 min read

Bu çözümün Türkçesi de var: sağ üstten dili TR yapın.

Overview

  • Challenge: Hidden message Part 3 (Hard)
  • Category: Audio Analysis / OSINT / Steganography
  • Flag Format: flag{Xxxxxx_Xxxxxx}

1. Initial Inspection & Audio Analysis

The challenge description highlighted leaving traces behind through sound, signals, and hidden messages within an audio waveform

Figure 1: Challenge 47 prompt on Discord with instructions and the target flag format
Figure 1: Challenge 47 prompt on Discord with instructions and the target flag format

Upon downloading and playing Hidden message.wav, the distinct rhythmic beeps immediately revealed that the audio stream contained Morse code.

2. Decoding the Morse Signal

Rather than manually transcribing the dits and dahs across the waveform timeline, I performed a quick search on Google for automated tools

Figure 2: Google search results identifying the Morse Code World decoder tool
Figure 2: Google search results identifying the Morse Code World decoder tool

I selected the adaptive audio decoder on Morse Code World (morsecode.world), uploaded Hidden message.wav, and processed the file. The tool successfully translated the embedded Morse audio into readable text

EVERY CONTACT LEAVES A TRACE
Figure 3: Morse Code World adaptive decoder displaying the decoded message: "EVERY CONTACT LEAVES A TRACE"
Figure 3: Morse Code World adaptive decoder displaying the decoded message: "EVERY CONTACT LEAVES A TRACE"

3. Contextual Research & Finding the Flag

Submitting variations of the decoded phrase directly led to a couple of rabbit holes due to the strict flag{Xxxxxx_Xxxxxx} format requirement. Investigating the phrase itself:

“Every contact leaves a trace.”

A quick query linked this quote directly to the foundational forensic concept known as Locard’s Exchange Principle

The principle was formulated by French criminologist Edmond Locard. Aligning the originator’s name with the required two-word title-cased format completed the puzzle:

  • Flag: flag{Edmond_Locard}

Connect & Follow

Originally published on Substack