Abstract
In this paper, we study the Lorenz chaotic system as a cryptosystem stream cipher. The system employs a stream cipher, in which the encryption key changes in a chaotic manner over time. For added security, one of the Lorenz generator's parameters are controlled by step function subsystem. The cryptosystem's bit stream passed the statistical randomness test. As a result, a cryptosystem's design can withstand many sorts of attacks, such as brute force. The system's key size will be greater than 256, allowing for a total of 2256 key spaces. As a result, the large key space will give strong plaintext security against a brute force attack.