Emails between Wei Dai (戴维) and Satoshi Nakamoto (中本聪)

Email 1

From: "Satoshi Nakamoto" <satoshi@anonymousspeech.com>
Sent: Friday, August 22, 2008 4:38 PM
To: "Wei Dai" <weidai@ibiblio.org>
Cc: "Satoshi Nakamoto" <satoshi@anonymousspeech.com>
Subject: Citation of your b-money page

I was very interested to read your b-money page.  I'm getting ready to
release a paper that expands on your ideas into a complete working system.
Adam Back (hashcash.org) noticed the similarities and pointed me to your
site.

I need to find out the year of publication of your b-money page for the
citation in my paper.  It'll look like:
[1] W. Dai, "b-money," http://www.weidai.com/bmoney.txt, (2006?).

You can download a pre-release draft at
http://www.upload.ae/file/6157/ecash-pdf.html  Feel free to forward it to
anyone else you think would be interested.

Title: Electronic Cash Without a Trusted Third Party

Abstract: A purely peer-to-peer version of electronic cash would allow
online payments to be sent directly from one party to another without the
burdens of going through a financial institution.  Digital signatures
offer part of the solution, but the main benefits are lost if a trusted
party is still required to prevent double-spending.  We propose a solution
to the double-spending problem using a peer-to-peer network.  The network
timestamps transactions by hashing them into an ongoing chain of
hash-based proof-of-work, forming a record that cannot be changed without
redoing the proof-of-work.  The longest chain not only serves as proof of
the sequence of events witnessed, but proof that it came from the largest
pool of CPU power.  As long as honest nodes control the most CPU power on
the network, they can generate the longest chain and outpace any
attackers.  The network itself requires minimal structure.  Messages are
broadcasted on a best effort basis, and nodes can leave and rejoin the
network at will, accepting the longest proof-of-work chain as proof of
what happened while they were gone.

Satoshi

Email 2

Hi Satoshi. b-money was announced on the cypherpunks mailing list in 1998.
Here's the archived post:
http://cypherpunks.venona.com/date/1998/11/msg00941.html

There are some discussions of it at
http://cypherpunks.venona.com/date/1998/12/msg00194.html.

Thanks for letting me know about your paper. I'll take a look at it and let
you know if I have any comments or questions.

Email 3

From: Satoshi Nakamoto
Sent: Saturday, January 10, 2009 11:17 AM
To: weidai@weidai.com
Subject: Re: Citation of your b-money page

I wanted to let you know, I just released the full implementation of the
paper I sent you a few months ago, Bitcoin v0.1.  Details, download and
screenshots are at www.bitcoin.org

I think it achieves nearly all the goals you set out to solve in your
b-money paper.

The system is entirely decentralized, without any server or trusted
parties.  The network infrastructure can support a full range of escrow
transactions and contracts, but for now the focus is on the basics of
money and transactions.

There was a discussion of the design on the Cryptography mailing list.
Hal Finney gave a good high-level overview:
| One thing I might mention is that in many ways bitcoin is two independent
| ideas: a way of solving the kinds of problems James lists here, of
| creating a globally consistent but decentralized database; and then using
| it for a system similar to Wei Dai's b-money (which is referenced in the
| paper) but transaction/coin based rather than account based. Solving the
| global, massively decentralized database problem is arguably the harder
| part, as James emphasizes. The use of proof-of-work as a tool for this
| purpose is a novel idea well worth further review IMO.

Satoshi