All concepts
Concept
Consensus
Distributed Timestamp Server
First appeared Oct 2008
Why it matters
This is the conceptual heart of the white paper — ordering transactions in time is exactly what prevents double-spending, and the chain of timestamps is what we now call the blockchain.
What it is
Satoshi's framing of the blockchain: a server that takes a hash of items to be timestamped and publishes it, with each timestamp including the previous one, forming a chain.