Wei Dai describes b-money: money for pseudonyms, where every participant keeps their own ledger of who owns what, and new money is created by computational work. Ten years later, the Bitcoin whitepaper cites b-money as its first reference.

Source

Fact · Wei Dai, “b-money” (weidai.com/bmoney.txt): protocol 1 – every participant maintains a separate database of how much money belongs to each pseudonym; money is created by solving computational problems. Announced on the Cypherpunks list, 26 November 1998. Bitcoin whitepaper (2008), reference [1].

Open source · weidai.com ↗

The question on the back

How many agreements in your life rest only on the other person’s word?