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Handbook of Multimedia for Digital Entertainment and Arts- P7

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Handbook of Multimedia for Digital Entertainment and Arts- P7: The advances in computer entertainment, multi-player and online games, technology-enabled art, culture and performance have created a new form of entertainment and art, which attracts and absorbs their participants. The fantastic success of this new field has influenced the development of the new digital entertainment industry and related products and services, which has impacted every aspect of our lives. | 7 Countermeasures for Time-Cheat Detection in Multiplayer Online Games 169 be accomplished based on estimations of network latencies and by exploiting the information contained within transmitted messages 17 18 . The scheme is called Algorithm for Cheating Detection by Cheating AC DC 16 17 . To briefly outline the idea behind the scheme AC DC consists on the exploitation of a counterattack to be performed against a suspected node in order to verify if such a peer can be recognized as a cheater. More specifically at a given time only one peer is enabled to perform the counterattack. We call such peer the leader peer Pl. Of course mechanisms should be enabled to make sure that eventually a node chosen as a leader is not a cheater. Hence such role should be passed among peers as discussed more in detail in the following. Once the leader Pl wants to control a suspected node Pl increases the transmission latency of events generated at Pl for Pi. Pl starts the counterattack by continuously computing a measure of the average latency from pi to Pl. Such measure is obtained by taking into account values of 8il e k for events coming from Pi lil ek WTrec ek C df - WTic k . 8 In 8 WTrlec e k represents the time of reception of e k at Pl WTic e k is the possibly cheated wallclock time at which Pi claims that eki has been generated and drifts is the drift between physical clocks of the two peers. Such values 8il e k can be averaged or manipulated through a low-pass filter to smooth the variable behaviour of latencies 20 22 25 28 so as to have a value of the latency from the suspected node to the leader. The counterattack that Pl exploits against Pi consists in the delay of the transmission of each novel event el generated by Pl towards Pi. Such transmission is delayed for an amount of time X. Concurrently new latency values 8il e k are collected at Pl for a given time interval. These measurements are averaged to obtain a novel estimation of the average latency from Pi to Pl. The