Adam Back

Adam Back is a British cryptographer and cypherpunk, best known for inventing Hashcash in 1997, a proof-of-work system for fighting email spam.

Hashcash is cited in Bitcoin: A Peer-to-Peer Electronic Cash System, and it influenced the Proof-of-Work mining used by Bitcoin. He's the co-founder and CEO of Blockstream, a Bitcoin technology company.

Some people speculate that he's Satoshi Nakamoto, which he has denied.