Adam Back
Adam Back: Inventor of Hashcash, cited in the Bitcoin whitepaper; co-founder and CEO of Blockstream. Cypherpunk and cryptographer. In 1997 he proposed Hashcash, the proof-of-work that Bitcoin mining uses. In 2008 Satoshi emailed him before publishing the whitepaper, and he pointed Satoshi to Wei Dai's b-money. In 2024 he testified in COPA v Wright.
Source: bitcoindefense.org
Key facts
| Fact | Value | Source |
|---|---|---|
| Also known as | @adam3us | bitcoindefense.org |
| Role | Inventor of Hashcash, cited in the Bitcoin whitepaper; co-founder and CEO of Blockstream | bitcoindefense.org |
| First known Bitcoin link | Received Satoshi's first known email, 20 Aug 2008 | bitcoindefense.org |
| In the Bitcoin whitepaper | Cited as reference [6] | bitcoin.org/bitcoin.pdf |
| Location | Malta (public X profile) | x.com |
| Education | University of Exeter, PhD in computer science (distributed systems) | en.wikipedia.org |
| Work | Blockstream, co-founder (2014) and CEO | blog.blockstream.com |
Background
- Zero-Knowledge Systems (privacy technology, with Austin Hill) [realventures.com]
- “ecash, privacy tech, crypto, distributed systems” (his words, 2013) [bitcointalk.org]
Timeline
- 21 Aug 2008: Replied to Satoshi: the citation looks right; pointed him to Wei Dai's b-money. [bitcoindefense.org]
- 31 Oct 2008: The Bitcoin whitepaper cites Hashcash as reference [6]. [bitcoin.org]
- 22 Oct 2014: Co-authors the pegged sidechains paper; Blockstream announces its $21M seed round on 17 Nov. [blockstream.com]
- 27 Sept 2018: Blockstream's Liquid sidechain produces its first block (launch announced 10 Oct). [blog.blockstream.com]
- 14 Mar 2024: Testifies in COPA v Wright; the court rules that Craig Wright is not Satoshi. [judiciary.uk]
- 23 Oct 2026: Upcoming: “From Hashcash to Bitcoin” fireside chat at Plan ₿ Forum, Lugano. [planb.lugano.ch]
Connections
- Satoshi Nakamoto: Satoshi emailed him on 20 Aug 2008; he replied on 21 Aug and pointed to b-money [bitcoindefense.org]
- Wei Dai: Pointed Satoshi to Wei Dai's b-money, which became reference [1] [gwern.net]
- Gregory Maxwell: Blockstream co-founders (2014) [blog.blockstream.com]
- Pieter Wuille: Blockstream co-founders (2014) [blog.blockstream.com]
In their own words
“Heres a bit of perl code which implements RSA encryption and decryption and is small enough to use for a signature” (9 Mar 1995, via cypherpunks mailing list) [cypherspace.org]
“The idea of using partial hashes is that they can be made arbitrarily expensive to compute (by choosing the desired number of bits of collision), and yet can be verified instantly.” (28 Mar 1997, via cypherpunks mailing list) [hashcash.org]
“Hashcash is free, all you've got to do is burn some cycles on your PC.” (28 Mar 1997, via cypherpunks mailing list) [hashcash.org]
“The hashcash CPU cost-function computes a token which can be used as a proof-of-work.” (1 Aug 2002, via paper) [hashcash.org]
“In fact I believe it was me who got Wei Dai's b-money reference added to Satoshi's bitcoin paper when he emailed me about hashcash back in 2008.” (18 Apr 2013, via BitcoinTalk) [bitcointalk.org]
Plan ₿ Forum Lugano 2026: sessions
Adam Back is on the official agenda of Plan ₿ Forum 2026 (Palazzo dei Congressi, Lugano, 23–24 October 2026) with 1 session. Times are local Lugano time with London time in brackets; the organiser can still move sessions on the day.
23 Oct, 10:30 Lugano (09:30 London): "From Hashcash to Bitcoin: Adam Back’s Cypherpunk Journey" (Fireside chat · WAGMI Stage · 30 min), with Aaron van Wirdum
Source: the organiser's agenda feed [Brella] and [official agenda], checked 2026-10-21. Full schedule and other speakers: Plan ₿ Forum 2026 event page.
FAQ
- Who is Adam Back?
- Adam Back: Inventor of Hashcash, cited in the Bitcoin whitepaper; co-founder and CEO of Blockstream. Cypherpunk and cryptographer. In 1997 he proposed Hashcash, the proof-of-work that Bitcoin mining uses. In 2008 Satoshi emailed him before publishing the whitepaper, and he pointed Satoshi to Wei Dai's b-money. In 2024 he testified in COPA v Wright. (source: bitcoindefense.org)
- What did Adam Back invent?
- In 1997 he proposed Hashcash, the proof-of-work that Bitcoin mining uses. (source: bitcoindefense.org)
- When did Adam Back first appear in Bitcoin's history?
- Received Satoshi's first known email, 20 Aug 2008. (source: bitcoindefense.org)
- Is Adam Back cited in the Bitcoin whitepaper?
- Yes. Adam Back is cited as reference [6] of the whitepaper (source: bitcoin.org).
- When does Adam Back speak at Plan ₿ Forum 2026?
- Per the official agenda (checked 2026-10-21): 23 Oct 10:30 Lugano (09:30 London): "From Hashcash to Bitcoin: Adam Back’s Cypherpunk Journey", WAGMI Stage. The organiser can still change times.
See also
- Satoshi NakamotoSatoshi Nakamoto: Creator of Bitcoin (pseudonym), active 2008–2011. Wrote the Bitcoin whitepaper (31 Oct 2008), mined the genesis block and released Bitcoin v0.1 (8 Jan 2009). Handed the project to other developers in December 2010 and stopped writing in April 2011. First known message: email to Adam Back, 20 Aug 2008.
- Wei DaiWei Dai: Computer engineer, author of b-money, reference [1] of the whitepaper. Described b-money in 1998: money created by solving computational problems and kept on pseudonymous accounts. Satoshi wrote that Bitcoin “expands on your ideas into a complete working system”. Announced b-money on the cypherpunks list, 27 Nov 1998 (UTC).
- Gregory MaxwellGregory Maxwell: Early Bitcoin developer; proposed CoinJoin (2013); co-founder of Blockstream (2014). In June 2011 he argued on the forum that Bitcoin should default to deterministic wallets; BIP32 later credits him with “the original idea of type-2 deterministic wallets”. In August 2013 he proposed CoinJoin for on-chain privacy. Blockstream's 2014 seed-round post lists him among its co-founders.
- Pieter WuillePieter Wuille: Bitcoin Core developer; author of BIP32 and co-author of SegWit, Schnorr and Taproot; Blockstream co-founder; now at Chaincode Labs. Author of BIP32, the hierarchical deterministic wallets behind today's seed phrases, and co-author of BIP141 (SegWit), BIP340 (Schnorr signatures) and BIP341 (Taproot). BIP32 (HD wallets), which he authored, is assigned, 11 Feb 2012.
- Bitcoin whitepaper“Bitcoin: A Peer-to-Peer Electronic Cash System” is the 9-page paper by Satoshi Nakamoto, sent to a cryptography mailing list on 31 October 2008. It proposes electronic cash without a trusted third party, using proof-of-work to solve double-spending. The PDF is at bitcoin.org/bitcoin.pdf.
- Aaron van WirdumAaron van Wirdum: OG at Bitcoin Magazine, Author of The Genesis Book, as listed by the organiser of Plan ₿ Forum 2026 in Lugano. Wrote The Genesis Book (Bitcoin Magazine Books, released 3 January 2024), the history of the digital-money projects before Bitcoin. At the forum: "From Hashcash to Bitcoin: Adam Back’s Cypherpunk Journey" (fireside chat, WAGMI Stage) on 23 Oct at 10:30 Lugano time (09:30 London), plus 1 more session.
- BlockstreamBlockstream describes itself as a Bitcoin and digital-asset infrastructure company 'building the foundations for the financial infrastructure of the future'. Its products include the Blockstream app (formerly Green), the Jade hardware wallet and the Liquid sidechain.
References
- bitcoindefense.org bitcoindefense.org
- X · @adam3us x.com
- cypherspace.org/adam cypherspace.org
- hashcash.org hashcash.org
- GitHub · adam3us github.com
- Bitcoin whitepaper (bitcoin.org) bitcoin.org
- en.wikipedia.org en.wikipedia.org
- blog.blockstream.com blog.blockstream.com
- realventures.com realventures.com
- bitcointalk.org bitcointalk.org
- cypherspace.org cypherspace.org
- hashcash.org hashcash.org
- hashcash.org hashcash.org
- blockstream.com blockstream.com
- blog.blockstream.com blog.blockstream.com
- judiciary.uk judiciary.uk
- planb.lugano.ch planb.lugano.ch
- gwern.net gwern.net
- Plan ₿ Forum 2026: official speakers page (planb.lugano.ch) planb.lugano.ch
- Plan ₿ Forum 2026: official agenda feed (Brella, PlanBLugano2026) api.brella.io