Secret SHenanigans

crypto network FCSC 2024 solved on

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Description

A crook skilled in technology is wary of proven secure channel protocols like SSH or TLS: “they’re all probably backdoored” he thinks. As he regularly needs to receive confidential information from his colleagues, he has developed his own secure channel establishment protocol, allowing anonymous clients to send confidential information to his server.

You have access to a network TAP positioning you as a Man-in-the-Middle between a client and the server, and you have also managed to grab the application’s source code (unfortunately without the server’s private key…). Can you recover the secret that the client sends to the server?

Files

Author

rbe

Challenge Instructions

  1. First, download docker-compose.yml:
    curl https://hackropole.fr/challenges/fcsc2024-crypto-secret-shenanigans/docker-compose.public.yml -o docker-compose.yml
  2. Launch the challenge by executing in the same folder:
    docker compose up
  3. Then, in another console, access the challenge with Netcat:
    nc localhost 4000
⚠️ Important: You must solve the challenge by interacting with the Docker container through the exposed network port. Any other way is not considered valid.

In case you encounter problems, please consult the FAQ.

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