I like teaching people, and I strongly believe in learning by solving challenges. That’s why I’ve prepared quite a few CTF-like tasks teaching security basics - like cryptography.

They are meant to be used as a part of lecture, but have enough context to be solvable without a formal introduction.



Your task is to predict the next number generated by this RNG.

Symmetric Ciphers

They say that “encryption is not authentication”. Prove them right by circumventing the simulated “session” mechanism implemented using various encryption methods.