The purpose of this research is to improve cryptographic security and processing efficiency by introducing a branching structure into chaotic stream cipher, thereby adding more nonlinearity to the overall system. The rapid advancement of IoT technology, has created a need for fast and secure cryptosystems suitable for environments with limited computational resources. Therefore, chaotic stream cipher based on deterministic chaos have been proposed, with security further enhanced through the introduction of Volterra filters and nonlinear functions to increase mathematical complexity. In contrast, this study proposes a new method that introduces a branching structure dynamically selected at runtime, rather than using a fixed equation to determine the internal state variables. This is expected to increase the system’s structural complexity, even in low-computing-resource environments, while enhancing security and maintaining efficient key usage and processing speed.