In the fourth email of the chain, Adam Back’s second reply suggested another related paper: “PayWord and MicroMint” by Ron Rivest and Adi Shamir (1996), which proposed extracting k-way hash collisions for digital coin scarcity rather than the partial pre-images used by Hashcash and later by Bitcoin. The load-bearing self-admission in this email — the line Back later cited in the Cointelegraph interview as “probably my biggest mistake” — was:
Sorry still not read your paper yet,
Despite being among the first people Satoshi contacted, Back did not engage with the attached draft at this point. The chain went silent for nearly five months until Satoshi wrote again on 2009-01-10 — the day after Bitcoin’s v0.1 release. Back would not actively engage with Bitcoin until 2013; the broader story of that delay is documented in the Adam Back biography.