Proof of History whitepaper
Anatoly Yakovenko publishes the PoH whitepaper — proposing a sequential SHA-256 hash chain as a verifiable cryptographic clock. Reportedly conceived late one night in a San Francisco café, drawing on his Qualcomm work on Time Division Multiple Access for cellular networks and on Stanford research into Verifiable Delay Functions. At the time Bitcoin handles ~7 TPS and Ethereum ~13–15.