This book provides a comprehensive exploration of stochastic processes and their critical applications in enhancing physical layer security for modern communication systems. The book uniquely focuses on the intersection of advanced mathematical models and cutting-edge security techniques, making complex concepts accessible and practical for real-world applications. The book first presents a comprehensive theoretical study of stochastic processes and their applications in physical layer security. Guided by these theoretical foundations, the authors then offer practical design strategies to enhance the performance of communication systems and facilitate their implementation. The book equips researchers, engineers, and security professionals with the knowledge and tools to tackle contemporary challenges. By bridging the gap between theory and practice, the authors ensure that readers can implement effective security measures in the ever-evolving landscape of modern communications. Comprehensively clarifies stochastic process concepts including convergence modes, resolving nomenclature confusion across different textbooks that frequently obscures fundamental understanding; Specializes in physical layer security applications, offering cutting-edge strategies beyond traditional encryption methods; Combines principles from probability theory, information theory, and communication systems for a comprehensive view.