How Blockchain works Pt II
To generate an output hash with desired amount of 0’s in the beginning, miners will add “nonce”. Nonce is a number/ value that can only be used once. The nonce will be put inside the block before running it through the algorithm.
As small changes to input will completely change output, miners usually try random nonces until they find a valid output hash.
Once block is mined, miner broadcasts the newly mined block to all other miners. Then, they will check the block is valid so they can add that to their version of the blockchain and transaction is complete.
However, in block, miners needs to include output hash from previous block so they are all connected, which is why they are called a blockchain.
Every miner has their own version of the blockchain inside their computer and everyone trusts the blockchain that has the most computational work put into it also known as the miner with the longest blockchain.
If a miner changes a transaction in the previous block, the output hash will also change and so does the block that leads to the other hashes. In this situation, miner will have to redo the work for the rest except his.
So even if a miner wanted to cheat, he will need more than 50% of his networks computing power and that is unlikely to happen. Network attacks/ cheats like these are called 51% attacks.
Source: https://academy.binance.com/en/glossary/blockchain
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