How to Protect Peer-to-Peer Online Games from Cheats

Recently, P2P (peer-to-peer) online game systems have attracted a great deal of public attention. They work without central servers, thus, the maintenance and organization costs have been drastically reduced. However, in P2P systems, it is difficult for game creators to prevent cheats by malicious players, due to the lack of trusted servers. In order to solve the problem, we propose a practical and secure protocol based on public key cryptography, suitable for such P2P online game systems. Our scheme guarantees that players can immediately detect when cheating by other malicious players happens, and that honest players can prove their innocence, on condition that more than half of the participants are honest. We categorized cheating into four groups, Crack-The-Game-Software attack, Change-The-Input-After-Communication attack, ForgeThe-Result attack and Be-Offline-When-Losing attack, and proved that our system is secure against each attack. Moreover, we showed that our scheme is general and directly applicable to almost all of existing online games including simulation games, fighting games, and MMORPG.