This book offers an in-depth exploration of the application of blockchain and smart contract technologies in the field of cybersecurity. It begins by defining the fundamentals of cybersecurity in the context of blockchain and smart contracts, and then moves on to the world of e-government services, describing how blockchain can enhance the security of these services. The book also explores how blockchain can secure the Internet of Things (IoT), focusing on applications such as securing drones and protecting robotic networks. The importance of scalability in distributed replication systems is also discussed, with a particular focus on sharding. Finally, the book looks at the challenges of data protection in distributed ledger and blockchain technologies, providing both an analysis of the problems and solutions. Written by academic researchers and industry experts, this book offers a comprehensive and nuanced perspective on the transformational potential of blockchain and smart contracts in the field of cybersecurity.