To be clear the entire blockchain is retained on this large network of computers, meaning that no one person has control over its history.    That?s an important component, because it certifies everything that has happened in the chain prior, and it means that no one person can go back and change things. It makes the blockchain a public ledger that cannot be easily tampered with, giving it a built-in layer of protection that isn?t possible with a standard, centralized database of information.