||Blockchain techniques (the core of cryptocurrencies such as Bitcoin) have reshaped the future of financial transactions and decentralized interactions. They are also expected to bring us a more self-organizing and dependent digital world. The abstraction of blockchain is very delicate. It relies on cryptography tools and decentralized system concepts to achieve an open, secure, and efficient system (such as Bitcoin). This course aims to introduce the concepts of blockchain techniques and applications, including Bitcoin and blockchain design, basic cryptography tools, decentralized networks and consensus, and blockchain applications.