Bitcoin is a crypto currency introduced by Satoshi Nakamoto in 2008. It has the features of decentralization cross-border and fixed total amount and has become one of the most widely used crypto-currencies. Bitcoin, as a new digital currency system, innovatively makes the use of cryptographic elements and consensus mechanisms and builds up a secure decentralized system. The Blockchain, as the core of Bitcoin, uses peer-to-peer network communications and backs up transaction data in every node of the system, thus creating a huge distributed public book. It is essentially a decentralized distributed ledger database, and the decentralization means that the transaction is broadcast to the entire network, where everyone is involved in book keep...