O-line Karma: Towards a Decentralized Currency for Peer-to-peer and Grid Applications (Brief Abstract)

P2P and grid systems allow their users to exchange information and share resources in a uniform and reliable manner. In an ideal world, users make roughly as much resources available as they use. In reality, this is not always the case, and some kind of currency or barter (called karma) is needed that can be exchanged for resources to limit abuse. P2P and grid systems are distributed systems without centralised control or hierarchical organisation. Unfortunately, all currency-like systems known require some kind of centralised control to manage security and to detect fraud (e.g. double spending). To solve this problem, we present a completely decentralised, o-line karma implementation for P2P and grid systems, that detects double spending and other types of fraud under varying adversarial scenarios. The system is based on the tracing of the spending pattern of coins, and distributing the normally central role of a bank over a predetermined, but random, selection of nodes. The system is designed to allow nodes to join and leave the system at arbitrary times 1 .