Research On H.264Video Encryption Algorithm

The video contain large amount of data, and the information delivered by video can be intuitive, accurate and easy to be understood and accepted. H.264is a new video encoding standard. Compared with the previous video standard, H.264has a higher compression efficiency and better network affinity. It gets more and more widely used, while also facing more and more security threat. Therefore, the encryption algorithm, which work together with the new H.264technology, is a key response to the video security threatsThe intra prediction residual and the motion vectors are two important kinds of video data. They are the main research object of the video encryption algorithm. The intra prediction residuals contain plentiful texture information. This dissertation proposes a new encryption algorithm combined with the H.264intra macroblock partitioning technique. The frequency domain PSNR for the16×16macroblock and the Weber coefficient for the4×4macroblock are used to filter out the eccrypted objects, which are similar to the plaintext image. Then the non-zero quantized coefficients are encrypted by stream keys in the CAVLC encoding phase. The stream keys are managed by two chaotic systems, which guarantee the random and security of the keys. The experiment showed that the algorithm have a good performance on the visual security, encryption speed, compression efficiency and the image quality.The motion vector contains plenty of motion trajectory information. Now the encryption algorithms of motion vector are always applied to enhance the security of intra encryption algorithm simply. The shortcomings of these algorithms include the small key space, the slow diffusion speed of encryption effect and the low security. In this thesis, the polar coordinate transformation is used to expand the key space. And the motion vector, which is satisfied with certain amplitude, is selected to be encrypted only. The experiment proved that the algorithm has fast diffusion speed, strong security and small influence on the compression efficiency.