Selective encryption of video transmissions over multi-hop wireless networks

From a user perspective both security and power consumption during video transmissions are critical. On the one hand, assuming an eavesdropper on the wireless link, the transmitted video should be encrypted so that the unauthorized user is not able to reconstruct it. On the other hand, depending on the strength and the type of cryptographic method used during information exchange, there is a corresponding power consumption overhead. Since encryption protocols are oblivious to the wireless channel conditions, all packets are encrypted regardless of the probability of them getting lost. However, if the application layer protocol received feedback from the link layer on the channel losses, the protocol could decide how much encryption effort is actually needed so that the eavesdropper cannot reconstruct the video clip successfully. To an eavesdropper packets lost due to interference or encrypted packets do not make any difference; both are invisible to the passive attacker. In this paper, we map the percentage of lost/encrypted packets to an objective video quality metric (PSNR). We also create a look-up table through experiments on real multi-hop video transmission traffic, which allows the application layer to adjust the amount of encryption performed.