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We present the design, implementation, and evaluation of PROMISE, a novel peer-to-peer media streaming system encompassing the key functions of peer lookup, peer-based aggregated streaming, and dynamic adaptations to network and peer conditions. Particularly, PROMISE is based on a new application level P2P service called <i>CollectCast</i>. CollectCast(More)
Multimedia data secmity is important for multimedia commerce. Previous cryptography studies have focused on text data. The encryption algorithms devdoped to secure text data may not be suitable to multimedia applications becattse of large data sizes and real time constraint. For multimedia applications, light weight encryption algorithms are attractive. We(More)
Several protocols have been proposed to defend against wormholes in ad hoc networks by adopting positioning devices, synchronized clocks, or directional antennas. In this paper, we propose a mechanism, MDS-VOW, to detect wormholes in a sensor network. MDS-VOW first reconstructs the layout of the sensors using multi-dimensional scaling. To compensate the(More)
—In this paper, some existing perceptual encryption algorithms of MPEG videos are reviewed and some problems, especially security defects of two recently proposed MPEG-video perceptual encryption schemes, are pointed out. Then, a simpler and more effective design is suggested, which selectively encrypts fixed-length codewords in MPEG-video bit streams under(More)
Privacy is needed in ad hoc networks. An ad hoc on-demand position-based private routing algorithm, called AO2P, is proposed for communication anonymity. Only the position of the destination is exposed in the network for route discovery. To discover routes with the limited routing information, a receiver contention scheme is designed for determining the(More)
This paper studies efficient and simple data broadcast in IEEE 802.15.4-based ad hoc networks (e.g., ZigBee). Since finding the minimum number of rebroadcast nodes in general ad hoc networks is NP-hard, current broadcast protocols either employ heuristic algorithms or assume extra knowledge such as position or two-hop neighbor table. However, the ZigBee(More)
This article presents a novel invisible robust watermarking scheme for embedding and extracting a digital watermark in an image. The novelty lies in determining a perceptually important subimage in the host image. Invisible insertion of the watermark is performed in the most significant region of the host image such that tampering of that portion with an(More)
It is expected that in the near future millions of users will have access to on-line distributed databases through mobile computers. This possibility raises challenging questions regarding the consistency and availability of data. To deal with the frequent, predictable and varying in degree disconnections that occur in a mobile environment, we introduce(More)
Checkpointing in a distributed system is essential for recovery to a globally consistent state after failure. In this paper, we propose a solution that benifits from the research in concurrency control, commit protocols , and site recovery algorithms. A number of checkpointing processes, a number of rollback processes, and computations on operational(More)