Every block must include these three things:
- A hash pointer to the previous block
- Timestamp
- List of transactions
Every block in a blockchain typically consists of the following elements:
- Block Header: This includes metadata about the block, such as its unique identifier (hash), timestamp, and a reference to the previous block’s hash.
- Transactions: This is a list of transactions that are being added to the blockchain. Each transaction contains information about the sender, receiver, amount, and any additional relevant data.
- Merkle Tree Root: A Merkle tree is a data structure that organizes transactions in a way that allows for efficient and secure verification of the data. The root of the Merkle tree is included in the block header.
- Nonce: A value included in the block header that, when hashed together with the other elements, produces a hash that meets certain criteria, such as being below a target value. Miners change the nonce value through a process called proof-of-work to find a valid block hash.
- Difficulty Target: This is a value in the block header that determines the level of difficulty for miners to find a valid block hash. It is adjusted periodically to maintain a consistent block creation time.
- Block Size and Version: Information about the size of the block and the version of the blockchain protocol being used.
These elements work together to ensure the integrity, security, and immutability of the blockchain. Each block is linked to the previous one through the reference to the previous block’s hash, forming a chain of blocks, hence the name “blockchain.”