Wiki / People / Adam Back

Adam Back

From the Bitcoin Takeover Wiki · ✓ 5 sources · 0 podcast anchors · built 2026-11-13

British cryptographer who invented Hashcash, co-founded Blockstream, and opposed Bitcoin XT's hard fork.

◆ Takeover vieweditorial · opinion, labelled

The wiki's angle: Back is the small-block side's most visible executive. Fork Wars records his August 2015 “2-4-8” suggestion, which complicates the idea that his side never offered larger blocks.[3]

Contents

  1. Cryptographer
  2. Block size war
  3. Satoshi speculation
  4. References

Cryptographer

Back was born in London in July 1970 and has a computer science PhD from the University of Exeter[1]. In 1997 he invented Hashcash; a similar system is used in Bitcoin[1]. He was one of the first two people to receive an email from Satoshi Nakamoto[1].

Block size war

Back criticised Bitcoin XT's 75% activation threshold as too low[2]. Fork Wars records an August 2015 tweet in which he suggested 2 MB, then 4 MB in two years and 8 MB in four[3]. He signed the December 2015 capacity roadmap and the February 2016 Hong Kong Roundtable statement, the latter as President of Blockstream[4][5].

Satoshi speculation

Several outlets have named Back as a possible Satoshi Nakamoto, and in 2026 an investigation by John Carreyrou in The New York Times asserted that he is; Back denied the allegation[1].

References

  1. secondaryWikipedia, “Adam Back” [archived]
  2. secondaryBitcoin Wiki (en.bitcoin.it), “Bitcoin XT” [archived]
  3. btkFork Wars: the block size war timeline (Bitcoin Takeover) [archived]
  4. primaryBitcoin Core, “Capacity increases for the Bitcoin system” (signatories), 21 Dec 2015 [archived]
  5. primaryBitcoin Roundtable, “Bitcoin Roundtable Consensus”, Medium, 20 Feb 2016 (Wayback Machine copy)

Related

Blockstream
The Bitcoin infrastructure company co-founded by Adam Back, Pieter Wuille and Gregory Maxwell in 2014.
Gregory Maxwell
Bitcoin Core developer behind CoinJoin and a Blockstream co-founder, central to the SegWit-first capacity road
Hong Kong Roundtable
The February 2016 meeting where miners and some Core contributors agreed SegWit first, then a roughly 2 MB har
Bitcoin XT
Mike Hearn's fork of Bitcoin Core that shipped BIP-101 in August 2015 and opened the public, client-versus-cli
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