Abstract: A purely peer-to-peerversion of electronic cash would allow online payments to be sent directly fromone party to another without going through a financial institution. Digitalsignatures provide part of the solution, but the main benefits are lost if atrusted third party is still required to prevent double-spending. We propose asolution to the double-spending problem using a peer-to-peer network. Thenetwork time stamps transactions by hashing them into an ongoing chain ofhash-based proof-of work, forming a record that cannot be changed withoutredoing the proof-of-work. The longest chain not only serves as proof of thesequence of events witnessed, but proof that it came from the largest pool ofCPU power. As long as a majority of CPU power is controlled by nodes that arenot cooperating to attack the network, they'll generate the longest chain andoutpace attackers. The network itself requires minimal structure. Messages arebroadcast on a best effort basis, and nodes can leave and re-join the networkat will, accepting the longest proof-of-work chain as proof of what happenedwhile they were gone.
Keywords: Cryptocurrency,Block chain, MinningRig, Bitcoin, E-Cash, Digital Cash, Bitcoin mining, PaymentNode.