Blockchains are divided into three categories according to how many people participate in the network: public chains (anyone can participate in maintaining this ledger), alliance chains (with access mechanisms), and private chains (similar to traditional centralized databases)

The subject matter involved in the blockchain: cryptography (hash digital signature, secure transmission and verification of information, ensuring the authenticity of transactions and difficulty in tampering), distributed computing and consensus protocols (how to allow everyone to jointly maintain and reach a consensus), Game theory (how to provide incentives to make people participate in accounting)