Blockchain is a growing (database) record, called block, which is connected and secured using cryptographic techniques. Each block usually contains cryptographic hashes from the previous block, timestamp, and transaction data.

By design, blockchain is resistant to data modification. Blockchain is "a distributed ledger (open ledger) that can record transactions between two parties efficiently and in a way that can be verified and permanent.

To use it as a distributed ledger, blockchain is usually managed by a peer-to-peer network collectively by following certain protocols for communication between nodes and confirming new blocks. After recording, the data in the block cannot be changed retroactively without changes in the next blocks, which requires consensus of the majority of networks.

Blockchain was designed from the start to be secure by design and is an example of a high-level distributed computing system with Byzantine Fault Tolerance (BFT). Decentralized consensus can be achieved with blockchain. This makes blockchain suitable for recording events, medical records and other record management activities, such as identity management, transaction processing, documentation of evidence, food traceability, and voting.

Blockchain was created by Satoshi Nakamoto in 2008 and is used as a big book for public transactions of bitcoin cryptocurrency. Blockchain discovery for bitcoin makes it the first digital currency to overcome the problem of double spending without requiring a trusted authority or central server. This bitcoin design has also inspired other applications.