The book introduces dependability (security metric) ideas, gives a general overview of the security analysis of Safety-Critical Systems (SCSs), explains why the study is necessary and defines key terms relevant to this research. It makes an effort to emphasize the significance of security in comparison to other dependability indicators and illustrates the key drivers of this research's purpose. The mathematical foundation of the security analysis process is briefly illustrated, and key mathematical terminology and concepts are presented that are crucial for the security evaluation of critical systems. This book's objective is to provide a thorough understanding of the security analysis process. It will be a research-focused book designed for undergraduate, graduate, and doctoral courses in software and cyber security. The fundamentals of reliability, security, metrics, and mathematical foundation have been covered in this book. Each technique's actual applications, along with benefits and drawbacks, are also shown. Applying each technique to the various case studies serves as a demonstration of how it works. By using the many case studies of safety-critical systems, the students can also learn different analysis approaches and how to model them. Students will be able to use these tools, in particular, on a case study of their choice to analyze system security. The book includes a comparison of various strategies and appropriate recommendations for further reading on these subjects. Moreover, this book's target audience includes software professionals who are interested in security analysis.