Improved perceptual video encryption using alternative unitary transforms

It has been demonstrated in our earlier work that perceptual video encryption can be effectively achieved by using alternative unitary transforms. In this paper, we extent our work by studying the importance of selecting rotation angles to be used to generate the alternative transforms. We show theoretically and experimentally that by selecting a set of rotation angles properly, the resulted perceptual encryption system will be operating without affecting the coding efficiency, but with a higher encrypting capability. In additional, our earlier algorithm can also be further simplified with the new set of rotation angles. Both objective and perceptive evaluation will be performed with the standard H.264 codec.