This practical new book offers the distributed-computing fundamental knowledge for individuals to connect with one another in a more secure and efficient way than with traditional blockchains. These new forms of secure, scalable blockchains promise to replace centralized institutions to connect individuals without the risks of user manipulations or data extortions. The techniques taught herein consist of enhancing blockchain security and making blockchain scalable by relying on the observation that no blockchain can exist without solving the consensus problem. First, the state-of-the-art of consensus protocols are analyzed, hence motivating the need for a new family of consensus protocols offering strong (deterministic) guarantees. Second, a didactic series of classic blockchain vulnerabilities is presented to illustrate the importance of novel designs better suited for the adversarial environment of open networks. These cutting-edge solutions are illustrated through the Redbelly blockchain design, which solves a different problem from the classic Byzantine consensus problem of 1982 and which deliversin the modern blockchain contexthigh performance at large scale. Topics and features: Covers the combination of security and distributed computing to devise the new generation of blockchains Shows how blockchain has shed new light on decades of research in distributed systems Provides instruction on the security needed by the industry to use blockchains in production Explains didactically the necessary ingredients to make blockchain efficient at large scale Helps fill the gap of knowledge in the highly demanded blockchain sector This unique volume contains the building blocks to design secure and scalable blockchains. As such, it is dedicated to developers, application designers, and computer scientists and requires only a minimal undergraduate level in mathematics and computer science. Vincent Gramoli is an Australian Research Council Future Fellow at the University of Sydney and the Chief Technology Officer of Redbelly Network. He teaches the Blockchain Scalability course on Coursera.