The blockchain is a growing record, called a block, that is connected and secured using cryptographic techniques.
Each block usually contains cryptographic hashes from the previous block, timestamp, and transaction data. By design, the blockchain is resistant to data modification. The blockchain is an openly distributed ledger that can record transactions between two parties efficiently and in a verifiable and permanent way. For its use as a distributed ledger, blockchain is usually managed by a peer-to-peer network collectively by following certain protocols for communication between nodes and confirming new blocks. Once recorded, the data in the block cannot be changed retroactively without changes to the next blocks, which requires the majority of network consensus.
The Blockchain is designed from the start to be safe (secure by design) and is an example of a distributed computing system with high Byzantine Fault Tolerance (BFT). A decentralized consensus can be achieved by blockchain. This makes the blockchain suitable for recording events, medical records, and other record management activities, such as identity management, transaction processing, evidence documentation, food traceability, and voting.
Blockchain was created by Satoshi Nakamoto in 2008 and used as a ledger for Bitcoin cryptocurrency public transactions. The discovery of the blockchain for bitcoin made it the first digital currency to overcome the problem of double-spending without requiring a trusted authority or centralized authority. This bitcoin design has also inspired other applications.