Prior to the release of bitcoin there were a number of digital cash technologies starting with the issuer based ecash protocols ofDavid Chaum and Stefan Brands. Adam Back developed hashcash, a proof-of-workscheme for spam control. The first proposals for distributed digital scarcity basedcryptocurrencies were Wei Dai's b-money and Nick Szabo's bit gold. Hal Finneydeveloped reusable proof of work (RPOW) using hashcash as its proof of work algorithm.
In the bit gold proposal which proposed a collectible market based mechanism for inflation control, Nick Szabo also investigated some additional enabling aspects including aByzantine fault-tolerant asset registry to store and transfer the chained proof-of-worksolutions.
There has been much speculation as to the identity of Satoshi Nakamoto with suspects including Dai, Szabo, and Finney – and accompanying denials.The possibility that Satoshi Nakamoto was a computer collective in the European financial sector has also been discussed. 