A blockchain — originally block chain — is a distributed database that maintains a continuously-growing list of ordered records called blocks. Each block contains a timestamp and a link to a previous block. By design blockchains are inherently resistant to modification of the data — once recorded, the data in a block cannot be altered retroactively.
Blockchains are secure by design and an example of a distributed computing system with high byzantine fault tolerance. Decentralised consensus can therefore be achieved with a blockchain. This makes blockchains suitable for the recording of events, title, medical records and other records management activities, identity management, transaction processing and proving provenance. This offers the potential of mass disintermediation and vast repercussions for how global trade is conducted.
Blockchain is one of the key technologies of Smart contracts.