2026-09-03
What Bitcoin Was Built On: Hashcash, b-money, and the Ideas Before Satoshi
Satoshi Nakamoto’s real achievement wasn’t inventing every idea inside Bitcoin. It was combining ideas that already existed, none of which had worked on their own, into something that finally did. The whitepaper itself credits several of them directly.
Hashcash: the proof-of-work piece
In 1997, cryptographer Adam Back created Hashcash — originally designed to fight email spam, not build a currency. The idea: force the sender’s computer to do a small, deliberately wasteful amount of computation before an email would be accepted, cheap enough for one real email, expensive enough to make mass spam impractical. Bitcoin’s mining is Hashcash’s proof-of-work concept, repurposed to secure a public ledger instead of filtering inboxes. Satoshi cites Back’s work directly in the whitepaper.
b-money: the ledger nobody actually built
In 1998, computer engineer Wei Dai published a proposal called b-money, describing a system where participants maintain records of how much money everyone owns, verified through computational puzzles, without a central authority. It was never actually implemented — b-money stayed a proposal, a sketch of what a decentralized digital currency could look like on paper. Satoshi references Dai’s work in the whitepaper’s opening lines, and later named the smallest unit of Bitcoin’s predecessor currency (before “satoshi” became the standard term) partly in a nod to this lineage.
Timestamping chains: proving something existed when you say it did
Cryptographers Stuart Haber and W. Scott Stornetta published work in the early 1990s on cryptographically timestamping documents — chaining hashes together so that altering an earlier record would break every timestamp after it, making tampering detectable. That’s structurally close to how Bitcoin’s blockchain works: transactions in one block are hashed together with the previous block’s data, so changing anything in the past would break the chain going forward. Satoshi cites their work too.
What Satoshi actually contributed
Nobody before Satoshi had combined proof-of-work, a shared public ledger, and a chained timestamp structure into a system that solved the double-spend problem without any central authority. Hashcash alone doesn’t create money. b-money never got built. Timestamp chains alone don’t prevent double-spending. Bitcoin’s real innovation was the specific combination — plus the incentive structure (mining rewards) that got a decentralized network of strangers to actually maintain it, with no company running the show.
Knowing the ingredients doesn’t answer whether the final dish is actually good money — that’s a separate, harder question, and it’s the one The Bitcoin Skeptic’s Guide spends 21 chapters actually working through.