The hash of a block must start with a certain number of zeros. The probability of calculating a hash that starts with many zeros is very low, therefore many attempts must be made. In order to generate a new hash each round, a nonce is incremented. See Proof of work for more information.
The Bitcoin Network Difficulty Metric The Bitcoin mining network difficulty is the measure of how difficult it is to find a new block compared to the easiest it can ever be. It is recalculated every blocks to a value such that the previous blocks would have been generated in exactly two weeks had everyone been mining at this difficulty. This will yield, on average, one block every ten minutes.
As more miners join, the rate of block creation will go up. As the rate of block generation goes up, the difficulty rises to compensate which will push the rate of block creation back down. Any blocks released by malicious miners that do not meet the required difficulty target will simply be rejected by everyone on the network and thus will be worthless.
The Block Reward When a block is discovered, the discoverer may award themselves a certain number of bitcoins, which is agreed-upon by everyone in the network. Currently this bounty is 25 bitcoins; this value will halve everyblocks. Fungibility Wallets and similar software technically handle all bitcoins as equivalent, establishing the basic level of fungibility.
The purpose of mining
Researchers have pointed out that the history of each bitcoin is registered and publicly available in the blockchain ledger, and that some users may refuse to accept bitcoins coming from controversial transactions, which would harm bitcoin’s fungibility. Bitcoin scalability problem The blocks in the blockchain were originally limited to 32 megabyte in size.
The block size limit of one megabyte was introduced by Satoshi Nakamoto in Eventually the block size limit of one megabyte created problems for transaction processing, such as increasing transaction fees and delayed processing of transactions.
Transactions contain some data which is only used to verify the transaction, and does not otherwise effect the movement of coins. SegWit introduces a new transaction format that moves this data into a new field in a backwards-compatible way.
What’s a hash function?
The segregated data, the so-called witness, is not sent to non-SegWit nodes and therefore does not form part of the blockchain as seen by legacy nodes. This lowers the size of the average transaction in such nodes’ view, thereby increasing the block size without incurring the hard fork implied by other proposals for block size increases.