A block chain or blockchain is a permissionless distributed database based on the bitcoin protocol that maintains a continuously growing list of transactional data records hardened against tampering and revision, even by operators of the data store's nodes. The initial and most widely known application of the block chain technology is the public ledger of transactions for bitcoin which would become the inspiration for similar implementations often known as altchains
The block chain is primarily tamper resistant through timestamping the hash of batches of recent valid transactions into "blocks", proving that the data must have existed at the time. Each block includes the prior timestamp, forming a chain of blocks, with each additional timestamp reinforcing the ones before it, thus giving the database type its name. Each block chain record is enforced cryptographically and hosted on machines working as data store nodes extending this validation to the network as a whole.