What is a block?
2023-04-12 08:34:21 UTC
In the context of blockchain technology, a block is a collection of data that contains a set of transactions, along with some additional information, that is cryptographically linked to the previous block in the chain. Blocks are the fundamental building blocks of a blockchain and serve as the permanent and tamper-proof record of all transactions that have occurred within the network.
A typical block contains the following components:
- Block header: The block header contains metadata about the block, such as:
- Version: Indicates the block structure's version.
- Previous block hash: A reference to the hash of the previous block in the chain, which creates the cryptographic link between blocks.
- Merkle root: A hash generated from the hashes of all transactions included in the block. The Merkle root allows for efficient and secure verification of the transactions within the block.
- Timestamp: A timestamp indicating when the block was created or mined.
- Difficulty target: A value representing the current mining difficulty in the network.
- Nonce: A random value used by miners to find a valid proof-of-work for the block.
- Transactions: A list of transactions that have been validated and included in the block. Transactions represent the transfer of assets or data between participants within the blockchain network. The first transaction in a block is typically a special transaction called the "coinbase" transaction, which rewards the miner for creating the block.
When a new block is created, or "mined," it is added to the blockchain, forming an ever-growing chain of blocks. The cryptographic link between blocks ensures the integrity and immutability of the blockchain since altering any block would require changing all subsequent blocks and redoing the proof-of-work for each of them, which is computationally infeasible.