Design And Implementation Of A Video Encryption Algorithm Based On H.264

Along with the rapid development of the mobile video apllications, monitoring applications and other multimedia video, video security has become a focus of attention.And so, encrypted video is one of the most direct and most convenient means of protecting video data. However, the traditional video encryption is distrbing the video data by bit arithmetic or numerical operations. Essentially there is little correlation between the generated key and plaintext, and the video data itself is still there in the ciphertext, only changes in the form, and it easy to crack in the case of the known ciphertext. I presented a extractive encryption algorithm by analyzing the various conventional video encryption algorithm. The major difference between the extractive encryption algorithm and the traditional encryption algorithm is the former extract a part of data which is greater impact on the video playback as a key directly and the remaining part is the ciphertext file. So this would have to make the whole explicit divided into two parts, the ciphertext and the key,and solved the problem by brute force when only knew the ciphertext. In additon, the key generated by different plaintext file has no connection because of the key data comes from plaintext file. And the same plaintext create a various encryption key on account of the random sequence created at different times. Therefore, for the security of the entire system has little effect when disclose a single key.I present a video stream data extraction rules on the basis of the analyzing H.264 codec rules: extracting the quantization parameter offset of the slice header, extracting the non I_PCM 4x4 luma prediction mode and the I_PCM pixel for the I slice data, extracting the motion vector residual information or symbol tailing factor of a P macroblock or B macroblock in the P slice or B slice. I designed a unit key file format according to the format of the extracted data,and encrypt the partial data on the macro-block selection through the random sequence generated by a random algorithm,and completing the ecnryption base on the H.264 stream parsing process.In the last, I testing and analysis of the effect of encryption. It can be drawn that the extractive encryption algorithm has a good encryption effect on the encryption video stream according to the experimental results of the analysis. In addtion, the encryption speed is fast because it takes only a entropy decoding process, and it has some application foreground and use value.