The encyclopedia · Software & IT · Technical decision · 2008
Bitcoin solved double-spending with a chain of proof-of-work
Nakamoto's 2008 whitepaper replaced the trusted bank with a proof-of-work chain: the longest chain is the ledger, and rewriting it costs real CPU.
Bitcoin (Satoshi Nakamoto)
The solution
Digital cash kept failing because the same coin could be spent twice unless a trusted party stopped it — a bank, or a double-spend protection server.
Nakamoto's proposal timestamps transactions by hashing them into a chain of hash-based proof-of-work: the longest valid chain wins, and altering history means redoing the proof-of-work.
The network needs minimal structure: messages are broadcast best-effort, nodes leave and rejoin at will, and each node accepts the longest proof-of-work chain as what happened while it was gone.
Why it worked
- Proof-of-work makes the majority of CPU power the arbiter.
- The chain's timestamping ties every block to all before it.
- No central party means no single point of failure or capture.
- Nodes verify independently, so trust is replaced by arithmetic.
What can be applied
If you can't appoint a trusted party, make dishonesty cost more than it can ever pay: tie consensus to a scarce resource attackers must outspend.
Aftermath
The whitepaper became the blueprint for the Bitcoin network, the first digital currency with widespread adoption — and its public ledger's privacy gaps drove later designs such as Zerocash.
Sources
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