[p2p-research] Bitcoin open source implementation of P2P currency

[Satoshi Nakamoto]

I've developed a new open source P2P e-cash system called Bitcoin.  It's 
completely decentralized, with no central server or trusted parties, 
because everything is based on crypto proof instead of trust.  Give it a 
try, or take a look at the screenshots and design paper:

Download Bitcoin v0.1 at http://www.bitcoin.org

The root problem with conventional currency is all the trust that's 
required to make it work.  The central bank must be trusted not to 
debase the currency, but the history of fiat currencies is full of 
breaches of that trust.  Banks must be trusted to hold our money and 
transfer it electronically, but they lend it out in waves of credit 
bubbles with barely a fraction in reserve.  We have to trust them with 
our privacy, trust them not to let identity thieves drain our accounts. 
  Their massive overhead costs make micropayments impossible.

A generation ago, multi-user time-sharing computer systems had a similar 
problem.  Before strong encryption, users had to rely on password 
protection to secure their files, placing trust in the system 
administrator to keep their information private.  Privacy could always 
be overridden by the admin based on his judgment call weighing the 
principle of privacy against other concerns, or at the behest of his 
superiors.  Then strong encryption became available to the masses, and 
trust was no longer required.  Data could be secured in a way that was 
physically impossible for others to access, no matter for what reason, 
no matter how good the excuse, no matter what.

It's time we had the same thing for money.  With e-currency based on 
cryptographic proof, without the need to trust a third party middleman, 
money can be secure and transactions effortless.

One of the fundamental building blocks for such a system is digital 
signatures.  A digital coin contains the public key of its owner.  To 
transfer it, the owner signs the coin together with the public key of 
the next owner.  Anyone can check the signatures to verify the chain of 
ownership.  It works well to secure ownership, but leaves one big 
problem unsolved: double-spending.  Any owner could try to re-spend an 
already spent coin by signing it again to another owner.  The usual 
solution is for a trusted company with a central database to check for 
double-spending, but that just gets back to the trust model.  In its 
central position, the company can override the users, and the fees 
needed to support the company make micropayments impractical.

Bitcoin's solution is to use a peer-to-peer network to check for 
double-spending.  In a nutshell, the network works like a distributed 
timestamp server, stamping the first transaction to spend a coin.  It 
takes advantage of the nature of information being easy to spread but 
hard to stifle.  For details on how it works, see the design paper at 
http://www.bitcoin.org/bitcoin.pdf

The result is a distributed system with no single point of failure. 
Users hold the crypto keys to their own money and transact directly with 
each other, with the help of the P2P network to check for double-spending.

Satoshi Nakamoto
http://www.bitcoin.org