Beep64

Challenge Description

Every CTF needs a base64 challenge... right?

Attachments

Solution

  • Unzip the file, we get a wav file which is 37 mins long

  • Listening to the audio file, it is DTMF tones

  • Online decoders dont work for such a long audio file

  • Using this repo we can decode the audio file

  • DTMF Output: out.txt

  • Removing the * and replacing with spaces

  • Decoding the rest using T9 Decoder

  • Replace

    • SPACE: nothing

    • ZERO: 0

    • ONE: 1

  • Decode using Binary and then Base64 decoding gives us the flag

Cyberchef Recipe

FLAG

flag{0421a964add97ff041431e2418e64508}

Resources

  • DTMF Decoder: https://github.com/ribt/dtmf-decoder

  • T9 Decoder: https://www.cachesleuth.com/vanity.html

  • Cyberchef: https://gchq.github.io/CyberChef/

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