What Is Blockchain?
A blockchain originally block chain is a continuously growing list of records called blocks, which are linked and secured using cryptography. Each block typically contains a hash pointer as a link to a previous block, a timestamp and transaction data. By design, blockchains are inherently resistant to modification of the data. A blockchain can serve as “an open, distributed ledger that can record transactions between two parties efficiently and in a verifiable and 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 validating new blocks. Once recorded, the data in any given block cannot be altered retroactively without the alteration of all subsequent blocks, which needs a collusion of the network majority.
A block commonly consists of four pieces of metadata:
- The reference to the previous block
- The proof of work, also known as a nonce
- The timestamp
- The Merkle tree root for the transactions included in this block.
Bitcoin Block Data (licensed under Creative Commons Attribution-Share-Alike 3.0 Unported, retrieved from Wikipedia)
Further Reading