Evaluation of selective encryption techniques for secure transmission of MPEG-compressed bit-streams

“Total” encryption of MPEG-I compressed bit-streams requires a large processing time. To reduce this processing time, Spanos and Maples (1996) propose encrypting only the data in the Intracoded frames. In this paper, experimental results are presented which indicate that Spanos and Maples´ method does not provide an adequate level of security. A better method that calls for encrypting all the Intra-coded macroblocks (I-MB´s) in all frames is then presented. Although this method achieves a 69% reduction in the processing time over “total” encryption, the motion content of the video sequence is apparent. Therefore, another method that calls for encrypting the headers of all predicted, macroblocks (MBs) in addition to encrypting the data in all I-MB´s is presented. Simulation results for this method show that the decoded video is fully disguised, but at the expense of decreasing the savings in the processing time to 21-60% of the processing time of “total” encryption