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Application-layer multicast (ALM) has recently emerged as a promising solution for diverse group-oriented applications. Unlike dedicated routers in IP multicast, the autonomous end-hosts are generally unreliable and even selfish. A strategic host might cheat about its private information to affect protocol execution and, in turn, to improve its individual benefit. Specifically, in a link-weighted ALM protocol where the hosts measure the distances from their neighbors and accordingly construct the ALM topology, a selfish end-host can easily intercept the measurement message and exaggerate the distances to other nodes, so as to reduce the probability of being a relay. Such distance cheating, rarely happening in IP multicast, can significantly impact the efficiency and stability of the ALM topology. To defend against this kind of cheating, we present a Vickrey-Clarke-Groves (VCG)-based cheat-proof mechanism in this paper. We demonstrate a practical mapping from the utility, payment, and welfare of a VCG mechanism to the link-weighted ALM context. Based on this, we further discuss practical issues for implementing the cheat-proof mechanism-specifically, a trustworthy distributed algorithm for payment computation. Performance analyses show that the overheads of the computation, storage, and communication of our implementation are controlled at low levels, and extensive simulations further testify the implementation's effectiveness. Although there are other similar studies in this area, the contribution of our cheat-proof mechanism and its implementation primarily lies in two aspects. On one hand, we first explicitly solve the distance cheating problem in link-weighted ALM since its proposal by mapping the VCG mechanism to link-weighted ALM context. On the other hand, our distributed implementation can not only effectively defend against distance cheating, but can also avoid the potential cheating behaviors when selfish ALM nodes fulfill the cheat-proof mechanism itself.