In peer-to-peer games, cheaters can easily disrupt the game state computation and dissemination, perform illegal actions and unduly gain access to sensitive information. We propose AntiCheat - a cheat detection and prevention protocol following a mutual verification approach complemented with information exposure mitigation. It is based on a randomized dynamic proxy scheme for both the dissemination and verification of actions and further reduces the information exposed to players close to the minimum required to render the game. We build a proof-of-concept prototype on top of Quake III. Experimentations with up to 48 players show that opportunities to cheat can be significantly reduced, even in the presence of colluding cheaters, while keeping good performance.