Bitcoin transactions are validated through a process called “mining”. This process involves multiple nodes on the network competing to validate the transaction by solving a complex mathematical problem. The node that solves the problem first gets to validate the transaction and add the block containing it to the blockchain.
The process of mining involves collecting a number of unconfirmed transactions into a “block” and then using computational power to solve a cryptographic puzzle associated with the block. The puzzle is designed such that it becomes progressively harder as the network’s computational power increases. Once a node solves the puzzle, it broadcasts the solution to the network, which verifies that the solution is correct. If the solution is indeed correct, the block is added to the blockchain and the transactions in the block are considered confirmed.
The cryptographic puzzle that must be solved is a double-SHA256 hash of the block header, which contains several pieces of information, including the previous block’s hash, the timestamp, and the nonce (a random number used to vary the output of the hash function). The network sets a target for the puzzle such that the hash of the block header must be less than or equal to the target in order for the block to be considered valid.
The node that solves the puzzle is also rewarded with a certain number of newly minted bitcoins (currently 6.25 bitcoins) as an incentive to participate in the network and validate transactions. This is how new bitcoins are introduced into the system.
The process of mining provides multiple benefits for the security and integrity of the Bitcoin network. First, it confirms transactions, ensuring that bitcoins can only be spent once. Second, it adds new blocks to the blockchain, preserving the historical record of all transactions on the network. Third, it makes it extremely difficult for a single actor to alter the blockchain, as doing so would require a tremendous amount of computational power.
To validate a transaction, the network checks that the inputs of the transaction (i.e., the bitcoins being spent) are unspent and belong to the person claiming to spend them. This is done by looking at the blockchain and verifying that the outputs of previous transactions that match the inputs of the current transaction are indeed unspent.
Once a block has been added to the blockchain, it cannot be altered without altering all subsequent blocks. This makes the blockchain tamper-evident and helps ensure the integrity of the system. The more blocks that are added to the blockchain, the harder it becomes to alter the history of transactions.
In conclusion, the process of mining is an integral part of the Bitcoin network, providing the means to validate transactions, add new blocks to the blockchain, and maintain the integrity of the system. The combination of cryptographic algorithms and a decentralized network of nodes ensures that the system is secure, transparent, and tamper-resistant.