Once a transaction is posted, the accuracy of the transaction must be confirmed by the blockchain network. Thousands of computers on the Blockchain work quickly to confirm that the details of the purchase are correct. After a computer verifies the transaction, the transaction is added to the blockchain block. Each block in the blockchain contains its own unique hash, along with the unique hash of the previous block. When the information in a block is edited in any way, the hash code of that block changes - however, the hash code on the block does not change after that. This contradictoriness makes it extremely difficult to change information on the blockchain without prior notice.