Difficulty:

Notes:

  • Neo takes the Red pill in the movie
    • "You take the blue pill – the story ends, you wake up in your bed and believe whatever you want to believe"
    • "You take the red pill – you stay in Wonderland, and I show you how deep the rabbit hole goes."

Rabbit Holes:

  • https://github.com/kimci86/bkcrack needs at least 12 Bytes of plaintext to brute-force.
    • We only have "\xcfCSCG{" (MSB from CRC is first byte)
      • Maybe brute-force other characters? Unlikely in a CTF
  • Comparison with original sound sample (reference_quote.wav) does not work
    • probrably modified? or from another source? online samples are all stereo

Solution:

  • Spectogram shows password Th3-R3D-P1ll?
  • steghide extract -sf matrix.wav -p Th3-R3D-P1ll? -xf output.png ergibt gültigen JFIF File
  • output.png has trailing PKZIP file (Header 50 4B 03 04)
    • stored in extracted_from_output.zip
  • extracted_from_output.zip has password-encoded file secret.txt
  • Google Search for "Oktoberfest Nacht" give original Image
    • Comparing original image with output.png shows differenzes in Lichterkette in bottom of the image
      • Color encodes Bit
      • Manually transposing gives 01101110 00100001 01000011 00110011 01011111 01010000 01010111 00111111 (and its complement)
      • Converting to ASCII gives Password n!C3_PW?
  • Decrypt secret.txt mit Password n!C3_PW? into secret_decrypt.txt
  • secret_decrypt.txt contains String 6W6?BHW,#BB/FK[?VN@u2e>m8
    • May be final flag (first and third letter are equal, fourth and last are unequal), but in non-standard encoding or simple substitution cipher
    • Trying out different simple encodings/ciphers on cryptii shows ASCII85 is used and flag is given in plaintext
  • WIN

Flag

CSCG{St3g4n0_M4s7eR}

Remediation: