【作者】 高阳；

【导师】 赵春晖；

【作者基本信息】 哈尔滨工程大学 ， 信息与通信工程， 2019， 硕士

【摘要】 视频作为一种信息载体,能够直观高效地传递信息,且信息容量大,在数字信息时代得到了广泛应用。同时由于互联网时代的来临,无线wifi与移动设备的飞速普及,网络环境安全面临着严峻挑战,视频信息泄露屡见不鲜。而另一方面社会各层面对信息隐私和信息安全的重视程度日益增强,保护视频信息安全势在必行。因此,视频加密技术也愈发受人重视。视频本身信息量大、数据结构复杂、实时性要求高,所以传统的将视频数据全部加密的手段已经不再适用,必须根据视频编码标准设计针对性的加密算法。本文基于当前国际最新视频编码标准——高效视频编码(High Efficiency Video Coding,HEVC),通过对熵编码进行详细研究,对HEVC编码的部分语法元素进行选择性加密。本文的主要研究内容有以下三部分:首先,对HEVC的自适应二进制算术编码(Context-based Adaptive Binary Arithmetic Coding,CABAC)模块进行了详细的研究,通过对HEVC语法元素的分析,找出适合加密的语法元素,提出了基于HEVC的选择性加密算法。为了保证码流兼容性,应对视频内容的相关语法元素进行加密。CABAC中二值化后的使用旁路编码模式的语法元素,由于格式标准、不牵涉上下文模型,适于进行加密处理。本文对五种二值化方式进行了详细分析,最终挑选了六个语法元素,使用RC6-CFB(Rivest Cipher 6-Cipher FeedBack)算法进行加密。实验结果满足了码流兼容性、安全性、压缩率不变性与实时性。其次,现有的加密算法为了保证HEVC的压缩性能对使用旁路编码的语法元素进行加密,语法元素的选择范围小;或是加密别的语法元素的同时降低了HEVC的编码性能。针对上述问题,本文提出了一种基于安全二进制算数编码(Binary Arithmetic Coding,BAC)的选择性联合加密算法,对常规编码模式中的二进制算术编码过程进行了加密。在旁路编码语法元素加密的基础上,选择了三个语法元素作为安全BAC的加密对象,实验结果加密效果良好,并且未添加额外码率,计算复杂度较低,保证了实时性。最后,对于不要求最高安全性的应用场景,加密算法在保证一定安全性的前提下应尽可能提高加密效率。本文对每个语法元素根据码字敏感度进行了加密优先级排序,缩小了语法元素的加密范围,最终选定了五个语法元素进行联合加密,提出了基于码字敏感度的联合加密算法。实验结果表明,该算法在满足了码流兼容性、安全性与压缩率不变性的前提下,进一步缩短了加密时间,提高了加密效率。更多还原

【Abstract】 Video,as an information carrier,can transmit information intuitively and efficiently,and has a large information capacity.It has been widely used in the digital information age.At the same time,due to the advent of the Internet era,the rapid popularization of wireless WiFi and mobile devices,network environment security is facing severe challenges,the leakage of video information is common.On the other hand,people are becoming conscious of information privacy and information security at all levels of society,so it is imperative to protect video information security.Therefore,video encryption has been paid more and more attention.Video itself has a large amount of information,complex data structure and high real-time requirement,so the traditional method of encrypting data is no longer applicable.It is necessary to design specific encryption algorithm according to video coding standards.In this paper,based on the latest international video coding standard-High Efficiency Video Coding(HEVC),some syntax elements of HEVC coding are selectively encrypted through a detailed study of entropy coding.The main contents of this paper are as follows:Firstly,the Context-based Adaptive Binary Arithmetic Coding(CABAC)module of HEVC is studied in detail.Through the analysis of HEVC grammar elements,the syntax elements suitable for encryption are found,and a selective encryption algorithm based on HEVC is proposed.In order to ensure the compatibility of video streams,the syntax elements related to video content should be encrypted.In CABAC,the syntax elements using bypass coding mode after binarization are suitable for encryption because of their standard format and no context model.Five binarization methods are analyzed in detail in this paper.Finally,six grammar elements are selected and encrypted by Rivest Cipher 6-Cipher FeedBack(RC6-CFB)algorithm.The experimental results meet the requirements of compatibility,security,compression rate invariance and real-time performance.Secondly,in order to ensure the compression performance of HEVC,the existing encryption algorithms encrypt the grammar elements using bypass coding,which have a narrow range of choices,or encrypt other grammar elements while reducing the encoding performance of HEVC.To solve the above problems,a selective joint encryption algorithm based on secure Binary Arithmetic Coding(BAC)is proposed,which encrypts the binary arithmetic encoding process in the regular encoding mode.On the basis of encrypting by-pass coding syntax elements,three syntax elements are selected as encrypting objects of secure BAC.The experimental results show that the encrypting effect is good,and no additional bit rate is added.The computational complexity is low,which guarantees real-time performance.Finally,for application scenarios that do not require the highest security,the encryption algorithm should improve the encryption efficiency as much as possible on the premise of ensuring certain security.In this paper,each syntax element is encrypted according to the sensitivity of the codeword,and the encrypted range of the syntax element is reduced.Five syntax elements are selected for joint encryption,and a joint encryption algorithm based on the sensitivity of the codeword is proposed.The experimental results show that the algorithm can further shorten the encrypting time and improve the encrypting efficiency on the premise of satisfying the compatibility,security and invariance of compression rate.更多还原