Adam Back

Adam Back is a British cryptographer and the CEO of Blockstream, one of the most influential companies in Bitcoin development. He is the inventor of Hashcash, the proof-of-work system published in 1997 that became a direct intellectual ancestor of Bitcoin's mining mechanism — Hashcash is one of only eight references cited in Satoshi Nakamoto's original Bitcoin whitepaper. Back earned his PhD in computer science from the University of Exeter, focusing on distributed systems and cryptography. He was an active member of the cypherpunk mailing list in the 1990s alongside figures like Wei Dai, Hal Finney, and Nick Szabo — the community from which Bitcoin's foundational ideas emerged. Hashcash was originally designed as an anti-spam mechanism: by requiring senders to compute a proof-of-work before sending email, it imposed a cost on mass mailing while remaining negligible for legitimate users. In 2014, Back co-founded Blockstream with a mission to advance Bitcoin's capabilities through sidechain technology. Blockstream developed the Liquid Network, a Bitcoin sidechain enabling faster settlements and confidential transactions for traders and exchanges. The company also contributed to Bitcoin Core development, lightning network infrastructure, and satellite-based Bitcoin broadcasting — a system that makes Bitcoin accessible without internet connectivity. Back is known for his conservative approach to Bitcoin development — prioritizing security, decentralization, and backward compatibility over feature velocity. In an industry that rewards novelty, Back's insistence on careful, incremental improvement of Bitcoin's base layer represents a philosophical commitment to the cypherpunk values that preceded crypto's commercialization.