With the development of information science and the computer technology

the application of video in commerce on the Internet

such as video on demand or video on line has become more and more common.At the same time

the demand for security becomes more and more urgent.According to the characteristics of the latest video compression standard H.264

this paper proposes several DCT-based encryption algorithms

conducts simulation on two standard video sequences

and analyzes and compares the quality of those proposed algorithms.The experimental results show that the proposed algorithms have no impact on the compression efficiency and have gained good encryption results with low complexity.The simulation results are all tested on JM(joint model

version 7.3) reference software

which is especially programmed for testing the coding standard of H.264.