Darknet is a free open source peer-to-peer electronic cash system that
 is completely decentralized, without the need for a central server or
 trusted parties. Users hold the crypto keys to their own money and
 transact directly with each other, with the help of a P2P network to
 check for double-spending.

 Full transaction history is stored locally at each client. This
 requires 1+ GB of space, slowly growing.