Bitcoin: A Peer-to-Peer Electronic Cash System

When trying to understand what Bitcoin is and does, it's helpful to start with an understanding of the context in which it was build and the problem it was trying to solve. There were many digital currencies before Bitcoin, but Bitcoin was the first decentralized digital currency. Creating a digital currency without a central authority was the problem that was being solved for. 

Bitcoin was first introduced to the world On October 31, 2008, with the publishing of the Bitcoin white paper Bitcoin: A Peer-to-Peer Electronic Cash System. The paper gives insight into the motivations and architecture of the system. Much of what is covered in the paper are topics that we will dive into in later units. So, we recommend reading through it briefly now and coming back to it often throughout your studies. 

Abstract

A purely peer-to-peer version of electronic cash would allow online payments to be sent directly from one party to another without going through a financial institution.  Digital signatures provide part of the solution, but the main benefits are lost if a trusted third 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 a majority of CPU power is controlled by nodes that are not cooperating to attack the network, they'll generate the longest chain and outpace attackers.  The network itself requires minimal structure.  Messages are broadcast 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.

Source: Satoshi Nakamoto, https://bitcoin.org/bitcoin.pdf
Public Domain Mark This work is in the Public Domain.