【摘要】 提出了一种随机改变熵编码码表来实现视频变长码字加密的方法.将熵编码码表中的码字按长度等特征分组,对视频内容信息事件序列做熵编码时,对应每一事件产生一个随机数确定其编码成同组内的哪一码字,随机数序列由二进制随机序列生成以保证随机性.该方法解决了密文出现非法变长码字的难题,保证密文格式兼容,不降低压缩率,达到序列密码的抗攻击强度且计算速度快10倍以上.实验证明密文画面不能理解,该算法适用于MPEG,H.26x及JPEG等主流编码信号.更多还原

【Abstract】 Video variable length codewords were encrypted by randomly changed variable length coding table while each codeword was coded.The codewords were grouped into the table according to their length.While coding the video event stream,a random number corresponding to every event was generated to decide which codeword in its group the event should be coded to.The randomness of the number sequence was ensured by generated from binary system random sequence.The difficult problem of generating forbidden codewords was solved while enciphering video in the algorithm.It can completely keep video coding format compliance and compression ratio.It has the same anti-attack strength as direct stream cipher method while its speed is over ten times faster than the latter to meet real-time requirement.The experiments show that the cipher pictures are fully disguised.The method can be applied to MPEG,H.26x,and JPEG signal,and can be made as a separate modular.更多还原