Since 2015,block chain technology,as the bottom technology of Bitcoin,has become a hot spot of research and application following Internet of Things,Cloud Computing,Big Data and Artificial Intelligence, and has been listed as one of the ten future development trends by Gartner. Block chain has several characteristics, such as decentralization,consensus mechanism,non-tampering, intelligent contract and so on. It is a new and decentralized computing paradigm. After analyzing and comparing research status of block chains at home and abroad, and briefly introducing the key technologies (principles...