Bitcoin a peer-to-peer electronic cash system

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-spenging problem using a peer-to-peer network.The network timestamps transactions by hashing them into an onging 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 evens witnessed.but proof that is came form the largest pool of CPU power/as long as a majority of CPU power is controlled by nodes that are not 

cooperation 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/////

Introduction 

commerce on the Internet has come to rely almost exclusively on financial institutions serving as trusted third parties to procerss electronic payments/ while the system works well enough for most transactions,it still suffers from the inherent weaknesses of the trust based model...

completely non-reversible transactions are not really possible,since financial institutions cannot avoid mediation disputes the cost of mediation increases transaction costs limiting the minimum pratical transaction size and cutting off the possibility for small casual transactions and there is a broader cost in the loss of ability to make non-reversible payments for non reversible services whth the possibility of reversal the need for trust spreads merchants must be wary of their customers hassling them for more information than they would otherwise need a certain percentage of fraud is accepted as unavoidable /those

costs and payment uncertainties can be avoided in person by using physical currency,but no mechanism exists to make payments over a communications channel without a trusted party

what is needed is an electronic payment system based on cryptographic proff instead of trust//allowing any two willing paries to transact directly with each other without the need for a trusted third party/transactions that are computationally impractical to reverse wold protect sellers from fraud /and routine escrow mechanisms could easily be implemented to protect buyers In this paper we propose a solution to the double-spending problem using a peer-to-peer distributed timestramp server to generate computational proof of the chronlogical order of transactions /the system is secure as long as hones nodes 

collectively control more cup power than any cooperation group of attacker nodes..