Blockchain formation. The main chain (black) consists of the longest series of blocks from the genesis block (green) to the current block. Orphan blocks (purple) exist outside main chain.
Bitcoin network data A blockchain, originally block chain, is a continuously growing list of records, called which are linked and secured using cryptography. Each block typically contains.
a blockchain is inherently resistant to modification of the data. It is «an open, distributed ledger that can record transactions between two parties efficiently and in a verifiable & permanent way». For use as a distributed ledger, a blockchain is typically managed by a peer-to-peer network collectively adhering to a protocol for inter-node communication and validating new blocks. Once recorded, the data in any given block cannot be altered retroactively without the alteration of all subsequent blocks, which requires collusion of the network majority.
Blockchains are secure by design and exemplify a distributed computing system with Byzantine fault tolerance.