The header contains metadata about a block. There are three different sets of metadata:
- The previous block hash. Remember that in a blockchain, every block is inherits this from the previous block. The previous block’s hash is used to create the new block’s hash. For every block N, we feed it the hash of the block N-1.
- Mining competition. For a block to be part of the blockchain, it needs to be given a valid hash. This contains the timestamp, the nonce and the difficulty. Mining is another crucial part of blockchain technology.
- The third part is a merkle tree root. This is a data structure that summarises the transactions in the block.
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