Cyber-physical systems (CPS) are engineered systems that are built from, and depend upon, the seamless integration of computational algorithms and physical components. CPS are characterized by a strong interconnection of various computing systems (and algorithms) that are used to control, monitor, and interact with physical processes, thus improving the overall capability, adaptability, scalability, resiliency, safety, security, and usability of the associated engineered system. CPS technology has also enabled several critical infrastruc-ture applications, such as smart grid and renewable energy systems, biomedical and health care, next-generation transportation, industrial automation, and defense systems. However, such Critical-Infrastructure CPS (CI-CPS) are extremely vulnerable to sophisticated cyber-attacks due to their interconnected nature. The consequences of malicious attacks may range from minor variation in performance to absolute inability to control the system, which may lead to catastrophic results for both the system operators and users. Ensuring security of system components, privacy of system or user data, and availability of services (provided by the system), are some of the most vital requirements of a CI-CPS. Previous works in the literature proposed many solutions to improve security, privacy and availability of CI-CPS. However, several critical open problems in these areas remain unaddressed. In this direction, the rst part of this dissertation addresses the problem of securing location discovery of wireless and mobile components (of a CI-CPS) by proposing a novel spread-spectrum-based approach to eliminate incorrect localization data injected by malicious location anchors. The second part of this dissertation presents a framework to increase the capacity (and consequently availability) of existing wireless networks, by utilizing a secondary cognitive radio network based approach. The third part and nal part of this dissertation presents a novel framework to enable privacy-preserving smart meter data reporting in a smart grid CI-CPS, with a minimal impact on data utility. The e ciency and e ectiveness of the proposed solutions are demonstrated by means of analytical evaluations and empirical results. The outcomes of this dissertation will further our current knowledge and understanding of the security, privacy and availability issues in this upcoming and nationally important area of CI-CPS.