Scott Stornetta
The physicist who, with Stuart Haber, built the first blockchain in 1991 — to prove when a document existed, not to move money.
At Bellcore in 1991, Stornetta and Haber published How to Time-Stamp a Digital Document: each timestamp carries the hash of the one before it, so nobody can quietly insert or alter a document later without breaking the chain. A year later they added Merkle trees, letting many documents share a single link.
To turn the idea into a business they founded Surety, which since 1995 has printed the chain's latest hash as a classified ad in the New York Times — a paper copy no one can hack after the fact. When Satoshi Nakamoto's whitepaper appeared in 2008, three of its eight references pointed to Haber and Stornetta.