Assertion Supported AI assessment confidence: 98% certainty 5/5 debate potential 1/5

Adam Back invented Hashcash, used in Bitcoin mining

Michael Copeland · a16z Podcast | Hard Forks, Hard Choices for Bitcoin · Jan 2, 2019 · at 1:08

Host Michael Copeland introduces cryptographer Adam Back, co-founder of Blockstream, on the a16z Podcast discussing Bitcoin scaling.

0:00 / 0:07exact quote · 7.1s

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“Back invented Hashcash, a proof-of-work system, which, among its other applications, is used in Bitcoin mining.”

quote is from the automated transcript, cleaned for reading: filler sounds and stutters are removed, nothing is rephrased. names can be misheard (the analysis reads context, assessments check outside sources). how →

The claim, plainly

Adam Back invented Hashcash, a proof-of-work system used in Bitcoin mining.

a quote alone can be ambiguous, so this restates it with the references and context of the conversation around it resolved. AI-written; the tape below the player is the source.

Assessment

Both legs of the claim are fully verified by historical documentation. Dr. Adam Back invented Hashcash in May 1997 (and formally published the specification in August 2002) as a proof-of-work cost function to combat email spam and DoS attacks. In the 2008 Bitcoin whitepaper ('Bitcoin: A Peer-to-Peer Electronic Cash System'), Satoshi Nakamoto explicitly cited Back's Hashcash paper and implemented Bitcoin's core proof-of-work consensus and mining mechanism based on the Hashcash partial hash collision algorithm.

Adam Back proposed Hashcash in May 1997 and authored the 2002 paper 'Hashcash - A Denial of Service Counter-Measure'.
Section 4 of Satoshi Nakamoto's 2008 Bitcoin whitepaper explicitly states Bitcoin uses a proof-of-work system similar to Adam Back's Hashcash and directly cites Back's paper as reference [6].

Checked against

[1] researchgate.net [2] bitcoin.org [3] medium.com [4] blockstream.com [5] bitstack-app.com [6] wikipedia.org [7] coingeek.com

Adam Back Hashcash 1997 Bitcoin whitepaper proof of work Bitcoin whitepaper reference Hashcash Adam Back proof of work

assessed as of 2026-08-27

This assessment is an AI reading of a public statement, made against the cited references with the confidence shown. It can be wrong. The quote, the tape and the references are all on this page; if something is off, use report an error below. full disclaimer →

Mentioned

Back Bitcoin mining Hashcash

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