The earliest documented email from Satoshi Nakamoto. Writing to Adam Back, Satoshi confirmed he was about to publish a paper that built on Hashcash and asked Back to verify the citation form he had drafted:
[A. Back, "Hashcash - a denial of service counter-measure,"
http://www.hashcash.org/papers/hashcash.pdf, 2002]The load-bearing line of the email reads:
Satoshi Nakamoto (email to Adam Back, August 20, 2008, 5:30:39 PM UTC)I’m getting ready to release a paper that references your Hashcash paper and I wanted to make sure I have the citation right.
Satoshi attached a link to a pre-release draft titled “Electronic Cash Without a Trusted Third Party” — the working title before the manuscript was renamed to “Bitcoin: A Peer-to-Peer Electronic Cash System” for the cryptography mailing-list draft where the abstract appears.
This is the earliest known direct contact between Satoshi and a central cypherpunk figure, and it is one of the primary-source observations underpinning the cypherpunk-independent-arrival analysis. Which precursors were in front of Satoshi on the day of this email, and which reached him only after, is dated precursor by precursor in what Satoshi knew before the code was done.
Adam Back replied the next day, confirming the citation and pointing Satoshi toward Wei Dai’s b-money proposal. Satoshi thanked him within hours, writing that “my ideas start from exactly that point”, and Back followed up minutes later with a second suggestion: Ron Rivest and Adi Shamir’s 1996 MicroMint paper.
Two days after the first email, Satoshi also wrote directly to Wei Dai to confirm the citation year (see the 2008-08-22 Satoshi → Wei Dai email).
The correspondence with Back resumed nearly five months later: the day after Bitcoin v0.1 was released, Satoshi wrote to him one final time to announce the launch.
The Adam Back identity hypothesis, the 2026 NYT Carreyrou investigation, and Adam Back’s own 2024 retrospective testimony each treat this email as the documented baseline of what Adam Back knew about Bitcoin’s design before its release. The email is also referenced in the Adam Back biography, the Satoshi biography, the Satoshi self-statements analysis, the Bitcoin design lineage analysis where the Hashcash citation Satoshi wrote becomes load-bearing evidence for the record of precursors he acknowledged, and the Satoshi activity timeline, where this email opens the chronological record of every documented Satoshi event.
