Blockchain is a cryptographically secure, distributed database consisting of linked, time-stamped blocks of data such as transactions. It is based on decentralized, peer to peer consensus and an incentive-driven model of security. Each bock in a blockchain contains a cryptographic hash of the previous block, which secures the integrity of the transaction data. The hash function, such as SHA-256, maps data to a bit string of a fixed size, a fingerprint of the original set of data. it is feasible to reverse the function to recover the original data, and any change in the input data results in a completely different hash. Hashes are stored in a deterministic Merkle tree data structures. Each full node in the network independently checks new blocks. Creators of new blocks that are accepted by the rest of the network are rewarded. The technology allows parties to transact reliably with other parties about whom they have no information, diminishing the need for trusted intermediaries, and this may cost you your job.