CrossCTF_2018: Lossy Oracle

Category: Crypto Points: 919 Description:

No one believes I can recover the message from this crappy ORacle. nc ctf.pwn.sg 1401 Creator - prokarius (@prokarius)

Write-up

Given the nature of this challenge, where the messages are essentially OR-ed with random data, it is needless to say that you can recover the original data by simply running the AND operation ever and over. This results in us getting the original file.

This process can be simplified with Python,

For a moment, I didn't know how to solve it but then I noticed that the final output data was just an MP3 file. Listening to it gives you the flag.

Therefore, the flag is crossctf{bitw1se0racl3}.

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