In recent years, massively multiplayer online games (MMOGs) have become very popular by providing more entertainment and sociability than single-player games. In order to prevent cheaters to gain unfair advantages in peer-to-peer (P2P)-based MMOGs, several cheat-proof schemes have been proposed by using digital signatures. However, digital signatures generally require large amount of computations and thus may not be practical to achieve real-time playability. We propose an Efficient and Secured Event Signature (EASES) protocol to efficiently sign discrete event messages. Most messages need only two hash operations to achieve non-repudiation and event agreement. The computation, memory, and bandwidth consumptions of EASES are low, which makes it applicable to P2P-based MMOGs.