Power-aware selective encryption of video transmissions in smart devices

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 an 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 between the sender and the receiver, 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 use a mathematical framework to quantify the effect of lost and encrypted packets on video quality (PSNR), and we design an algorithm that allows the application layer to adjust the amount of encryption performed depending on the channel´s signal-to-interference-and-noise ratio (SINR).