Inside PoW mining

The goal of mining is to find a block that is acceptable to the rest of the blockchain network. This block needs to have a header hash that is less than the difficulty threshold and contains only valid transactions.

A block header contains different values, such as the previous block hash, the hash of the transactions, a timestamp, and a nonce. The nonce is important because it allows miners to create block headers with different hashes. This is necessary because if all the hashes were very similar, it would be difficult to find a block that meets the requirements.

The security of the mining process depends on the security of the hash function used. If the hash function is weak or broken, it can compromise the security of the blockchain. It's important to assume that the hash function is secure when talking about attacks in blockchain.