This is a implementation of a correlation attack on a steam chipher. It attacks a given keysteam generator made by three LFSR's (Linear Feedback Shift Register) with given feedback polynomials and outputs the private key. The key consists of the initial states of these three LFSR's. Correlation attacks is the most important class of attacks on stream chiphers. Stream chiphers are commonly used for symmetric encryption. I believe that understanding cryptology is very important for a security mindset as an engineer.