Simply put, a blockchain is "an open, distributed ledger that can record transactions between two parties efficiently and in a verifiable and permanent way." More formally, a blockchain 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. Through the use of a peer-to-peer network and a distributed timestamping server, a blockchain database is managed autonomously. Blockchains are secure by design and inherently resistant to modification of the data: once recorded, the data in a block cannot be altered retroactively. This makes blockchains suitable for the recording of events, medical records, and other records management activities, identity management, transaction processing, and proving data provenance.
The first blockchain was conceptualised by Satoshi Nakamoto in 2008 and implemented the following year as a core component of the digital currency bitcoin, where it serves as the public ledger for all transactions. The invention of the blockchain for bitcoin made it the first digital currency to solve the double spending problem, without the use of a trusted authority or central server.