Blockchain

Each block contains data and a cryptographic reference to a prior block. Nodes validate rules and use a consensus protocol to decide which history to accept. Replication and consensus provide guarantees under defined assumptions.

Public networks may permit open reading and participation; permissioned networks restrict specified functions to authorized participants. Data is not encrypted by default, and published information can reveal relationships between addresses.

The record verifies what was published and how it changed. It does not itself establish an external event or physical object’s authenticity. Oracles, keys and governance remain relevant dependencies.