Notes

The bitcoin blockchain consists of a continuously growing list of unordered data records, called blocks.[citation needed]
Each block starts with a header, which contains Validation proof-of-work, a hash of the previous block's header, and a timestamp. All users verify a blockchain's correctness by checking the blockchain headers. If a user finds a block's proof-of-work to be invalid, he will not accept it and will replace it with the next block in the blockchain. Within a few minutes, the correct proof-of-work is accepted and a new block is created, containing a reference to the last correct block and some additional transactions. Additionally, transactions can be replaced, which produces an inconsistent blockchain, or even a blockchain fork.

Transactions that can no longer fit into a block are held in a transaction pool to be placed into a future block. This mechanism called "transaction malleability" limits the number of unconfirmed transactions in the blockchain.

Blocks are added to the blockchain by miners, using special bitcoin software running on dedicated bitcoin hardware devices known as ASICs. Miners maintain a copy of the blockchain,[217] and receive a transaction fee each time a block is added to the blockchain. Miners are not necessarily required to cache the entire blockchain, but they must be able to produce new blocks at almost exactly the difficulty target. Failure to do so results in the lost of their winning lottery ticket and a block reward payment. As of January 2016, the median block size was 1.4 MB.[218]: ch. An alternative implementation, Proof of stake, is actively being developed.

The transaction validation process is concerned with ensuring that all inputs are authorised. This is important to preserve the integrity of transactions and the blockchain as a whole. When a user sends a transaction, they digitally sign the transaction and hash it using a private cryptographic key. The input values are hashed as well. When the receiver inputs their signature into the bitcoin network, the resulting hash will have the same values as the original input and will verify that the receiver is the only one who can sign this transaction. That is, it must be linked to the receiver, which is true for all known inputs. https://free-solitaire.online/ If any input is changed, the signature becomes invalid, because the hash of the transaction will change.: ch. A transaction input is said to be authorised if it is owned by the signer, and not by someone else. After a transaction is validated, the digital signature is put into
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