Since media data in streaming media system are high volume and latency sensitive, transmission security of them have been a challenge task. To solve the problem, partial encryption and other media encryption schemes have been proposed. However those schemes are tradeoffs between security and efficiency. In a multi-stream system, using one media encryption scheme to protect all the media streams will induce either unscalability or insecurity. In this paper, the idea of partial encryption is generalized from encrypting a subset of one stream to multi-streams. A mathematical model based dynamic optimal selective control mechanism for multi-datastream security is proposed. Since the simplified model is 0-1 knapsack problem, which is NP-hard, a greedy heuristic incremental approximate algorithm is designed. Theoretical and experimental analyses show the performance of the algorithm is effective enough to support real-time applications. A prototype has been implemented in our Admire system, and used in a confidential project.
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