All concepts
Concept
Consensus
Proof of Work
First appeared Mar 1997
Why it matters
Proof of work makes rewriting history costly in real-world energy, which is what lets a decentralized network agree on one transaction order without trusting anyone.
What it is
A scheme in which producing a valid block requires finding an input whose hash falls below a target — work that is expensive to perform but trivial to verify. Bitcoin adapts Hashcash to chain blocks together.