This book provides a comprehensive overview of data security in cloud storage, ranging from basic paradigms and principles, to typical security issues and practical security solutions. It also illustrates how malicious attackers benefit from the compromised security of outsourced data in cloud storage and how attacks work in real situations, together with the countermeasures used to ensure the security of outsourced data. Furthermore, the book introduces a number of emerging technologies that hold considerable potential – for example, blockchain, trusted execution environment, and indistinguishability obfuscation – and outlines open issues and future research directions in cloud storage security. The topics addressed are important for the academic community, but are also crucial for industry, since cloud storage has become a fundamental component in many applications. The book offers a general introduction for interested readers with a basic modern cryptography background, and a reference guide for researchers and practitioners in the fields of data security and cloud storage. It will also help developers and engineers understand why some current systems are insecure and inefficient, and move them to design and develop improved systems.