基于随机分块和混沌技术的图像加密算法

发布时间：2019-03-25 21:40

【摘要】：图像是互联网上最主要的一种多媒体元素,政治、经济、国防、军事等方面均在广泛应用图像信息。在传输和使用图像过程中,国防、军事等应用领域均对图像内容的安全性有一定要求,迫切需要可靠安全技术以保证传输图像安全。针对这一方面的需求,研究人员提出了多种技术手段,其中图像加密便是一种行之有效的方案。图像加密又称图像置乱,是将一幅有意义的图像转换成一幅杂乱无章的图像,由于攻击者无法从杂乱无章的图像中获取有意义信息,从而保证图像信息的安全。本文以随机分块策略和混沌技术为主要切入点,研究新型图像加密算法,设计出三种有效的加密算法,取得了有意义的研究结果。论文先回顾了图像加密的发展现状,在此基础上,提出联合交换技术和随机分块的快速图像加密算法、基于块置乱和混沌映射的图像加密算法和基于混沌的多图像加密算法,具体研究结果如下。 1.提出联合交换技术和随机分块的快速图像加密算法该算法先用随机分块技术将图像分为四个重叠的图像块,再用密钥确定图像块的加密次序,最后依次运用像素交换技术对每个图像块加密并将计算结果写回图像。理论分析和实验结果表明,该算法可对任意大小图像实行有效加密,具有较好的安全性和鲁棒性。与经典Arnold变换相比,该算法的运行速度更快,安全性更高,应用范围更广。 2.提出基于图像块置乱和混沌映射的图像加密算法该算法先将输入图像随机分割成相互重叠的图像块,通过随机置乱图像块的位置达到对图像的初始加密,接着利用混沌映射和Arnold变换生成一系列安全的秘密矩阵,最后随机选择秘密矩阵与图像块进行异或操作,实现最终加密目的。实验结果表明,该算法运行速度快,安全性高,性能优于三种文献算法。 3.建立基于混沌映射的多图像加密算法针对多图像加密问题,研究了一次操作完成三幅图像加密的安全技术。该算法将三幅同尺寸的灰度图像看作一幅彩色图像的三个颜色分量,先用混沌技术生成安全的安全数据序列,接着与灰度图像进行异或计算,完成单幅图像的初始加密,然后将三幅初始加密图像拼接成一幅大图像,用交换技术打乱大图像中的像素位置,从而将三幅灰度图像的像素随机分布到彩色图像的三个分量中,最后将三幅加密图像组合成彩色图像即可完成加密目的。实验结果表明,该算法可将尺寸相同的三幅灰度图像转换成一幅安全的彩色秘密图像,加密后的图像文件大小比加密前的图像文件总容量要小,性能优于传统Arnold变换方法。
[Abstract]:Image is one of the most important multimedia elements on the Internet. Image information is widely used in politics, economy, national defense, military and so on. In the process of image transmission and use, the security of image content is required in the fields of national defense, military and other applications. Therefore, reliable security technology is urgently needed to ensure the security of image transmission. In response to this need, researchers put forward a variety of technical means, of which image encryption is an effective scheme. Image encryption, also known as image scrambling, is to convert a meaningful image into a chaotic image. Because the attacker cannot obtain meaningful information from the chaotic image, the security of the image information can be ensured. Taking random block strategy and chaos technology as the main starting point, this paper studies the new image encryption algorithm, designs three effective encryption algorithms, and obtains meaningful research results. Firstly, this paper reviews the development of image encryption, and then puts forward the joint exchange technology and random block fast image encryption algorithm, the image encryption algorithm based on block scrambling and chaotic mapping, and the multi-image encryption algorithm based on chaos. The specific results are as follows. 1. In this paper, a joint exchange technique and a fast image encryption algorithm based on random block are proposed. Firstly, the image is divided into four overlapping image blocks by random block technique, and then the encryption order of the image blocks is determined by the key. Finally, each image block is encrypted by pixel exchange technique, and the calculated results are written back to the image. Theoretical analysis and experimental results show that the proposed algorithm can encrypt images of any size effectively and has good security and robustness. Compared with the classical Arnold transform, the algorithm runs faster, safer and more widely used. 2. An image encryption algorithm based on image block scrambling and chaotic mapping is proposed. Firstly, the input image is randomly segmented into overlapping image blocks, and the initial image encryption is achieved by randomly scrambling the position of the image blocks. Then chaotic mapping and Arnold transform are used to generate a series of secure secret matrices. Finally the secret matrix and image blocks are randomly selected for XOR operation to achieve the final encryption purpose. The experimental results show that the proposed algorithm has the advantages of fast running speed, high security and better performance than the three literature algorithms. 3. In order to solve the problem of multi-image encryption, a multi-image encryption algorithm based on chaotic mapping is established, and the security technology of completing three images encryption at one time is studied. The algorithm regards three gray-scale images of the same size as three color components of a color image. Firstly, chaos technology is used to generate secure data sequences, then XOR calculation is carried out with gray-scale images to complete the initial encryption of a single image. Then the three initial encrypted images are spliced together into a large image, and the pixel positions in the large image are scrambled by the exchange technique, so that the pixels of the three gray-scale images are randomly distributed into the three components of the color image. Finally, three encrypted images can be combined into color images to achieve the purpose of encryption. The experimental results show that the algorithm can convert three gray-scale images of the same size into a secure color secret image. The size of the encrypted image file is smaller than the total capacity of the encrypted image file, and the performance of the algorithm is superior to the traditional Arnold transform method.
【学位授予单位】：广西师范大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TP309.7;O415.5

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