Timeless Melodies

Cryptography 150 pts Easy

Challenge Information

  • Challenge Name: Timeless Melodies
  • Category: Cryptography
  • Points: 150 pts
  • Teams Solved: 12
  • Description: "Blaise is excited to share his favourite classical composition with everyone. Join him and find the flag."
  • Note: Flag text consists only of lowercase letters and does not contain EOF{}. If the raw flag is "xyz", submit as EOF{xyz}
  • Files: tune.wav, a.txt (ciphertext)

Solution Methodology

Step 1: Initial Analysis

The mention of Blaise immediately brings to mind Blaise de Vigenère, hinting that a Vigenère cipher might be involved.

Files provided:

  • tune.wav - Audio file
  • a.txt - Contains ciphertext

Step 2: Audio Analysis

The tune.wav was the famous "Für Elise" by Ludwig van Beethoven superimposed with Morse code beeps.

Steps taken:

  1. Extracted the Morse code from the classic tune as beep.wav
  2. Used an online Morse code decoder to get the phrase

Decoded Morse Code:

"For wisdom names where fools mistrust."

Step 3: Analyzing the Hints

Key observations:

  • What does wisdom do? It Names
  • Name of the classical piece: Für Elise (a clue!)
  • The ciphertext: ybviemjrff (from a.txt)

Step 4: Vigenère Decryption

Attempted decryption with candidate keys:

  • wisdom, fools, blaise, classical, music, timeless, melody, piano
  • FurElise ← Success!

Decryption Process:

Ciphertext: ybviemjrff
Key:        FurElise
Method:     Vigenère Cipher Decryption

Vigenère Cipher Decryption

Using "FurElise" as the key to decode the ciphertext in a.txt successfully revealed the plaintext flag.

Decrypted Flag: (Wrap in EOF{})

The decrypted plaintext was all lowercase and needed to be wrapped in EOF{} format as specified in the challenge description.

Key Insights

Clue Analysis

  • "Blaise" → Blaise de Vigenère → Vigenère cipher
  • "Für Elise" → The classical piece name was the decryption key
  • "For wisdom names where fools mistrust" → Wisdom "names" the piece (Für Elise)
  • Morse code provided an additional layer of obfuscation

Tools Used

Tool / Command Purpose
strings tune.wav Check for embedded ASCII or hidden text
exiftool tune.wav Inspect metadata for keywords
sox / audacity Visualize frequency patterns and spectrogram
python3 For Vigenère decryption script
morse-coder.com Audio Morse code decoder

Multi-Layer Challenge

  1. Audio steganography (Morse code hidden in music)
  2. Cryptographic hint extraction
  3. Pattern recognition (Für Elise = key)
  4. Vigenère cipher decryption