Consensus All nodes must agree on additions to the blockchain ■ In a decentralized system like a blockchain system,there is no central coordinator (unlike the case for 2PC and 3PC) Categorization of consensus algorithms: ·Proof of Work Node needs to solve a cryptographic puzzle in order to add a block (more on next slide) ·Proof of Stake Node is chosen to add next block based on amount of currency held,with probability proportionate to stake ·Byzantine Consensus Node is chosen to add next block based on a message-passing- based consensus algorithm (more later) Database System Concepts-7th Edition 26.11 ©Silberscha乜,Korth and SudarshanDatabase System Concepts - 7 26.11 ©Silberschatz, Korth and Sudarshan th Edition Consensus ▪ All nodes must agree on additions to the blockchain ▪ In a decentralized system like a blockchain system, there is no central coordinator (unlike the case for 2PC and 3PC) ▪ Categorization of consensus algorithms: • Proof of Work ▪ Node needs to solve a cryptographic puzzle in order to add a block (more on next slide) • Proof of Stake ▪ Node is chosen to add next block based on amount of currency held, with probability proportionate to stake • Byzantine Consensus ▪ Node is chosen to add next block based on a message-passingbased consensus algorithm (more later)