基于混沌系统的图像加密算法研究

发布时间：2019-01-07 19:07

【摘要】：随着计算机和网络技术的快速发展,网络安全性问题也引起越来越多人的关注。而数字图像因其形象、直观与生动等特点,使其成为网络信息传输中的重要表达方式。然而由于数字图像具有数据量大,冗余度高,像素之间相关性强等特点,AES等传统的加密算法算法不再适合于图像加密。另一方面混沌系统因其具有对初始条件和控制参数的敏感性,周期点的稠密性以及拓扑传递性等特性,使其特别适合图像加密。近年来,大量的基于混沌的图像加密算法相继被提出。传统的加密技术大多基于一维混沌信号,由于这些加密技术具有密钥空间小,安全性低等缺点,因而这些加密算法存在着很大的缺陷。本文在此背景下将分数阶Chen系统与高维混沌系统应用于图像加密算法中,提高了算法的安全性和复杂度。本文主要工作和创新之处在于： 1.首先分析了混沌图像加密的国内外研究现状以及研究意义,详细的介绍了混沌理论以及密码学的基本知识,并对二者的关系进行了剖析。接下来对混沌图像加密算法的一般步骤以及评价指标进行了介绍。 2.提出了一种基于分数阶Chen系统的图像加密新算法。首先利用分数阶Chen系统产生所需的置乱序列；然后通过对明文信息的判断来完成行列置乱序列的选择,从而保证了其与明文的相关性；对置乱后的图像采用分组异或的算法对其像素值进行预处理,同时对预处理后的图像进行两轮像素加密,增加了算法的复杂度和安全性。最后通过与整数阶Chen系统算法进行比较可知该算法具有密文相关度低,密钥空间更大,安全性更高等优点。 3.基于超混沌系统的性质,提出了一种完全置乱方案的图像加密算法。首先利用超混沌系统产生所需的混沌序列,进而实现像素点位置的置乱；然后将以上所产生的置乱序列作为Logistic映射的密钥产生加密序列,增加了两过程之间的耦合性；此外单个点像素点之后以及之前加密完成的所有像素点灰度值之和被用来加密该像素值,保证了与明密文之间的相关性,从而能够有效的抵御已知／选择明文等各种攻击。理论分析及实验表明该算法具有密文相关度低,密钥空间更大,安全性高等优点。 4.基于数字图像具有数据量大,相邻像素之间的冗余度高等特性,为了提高算法的安全性,提出了一种基于分块的图像加密新算法。首先利用高维混沌系统产生四组混沌序列,同时将图像分为大小等同的四块,通过各块的明文信息确定对置乱序列的选择,进而实现对图像的置乱。然后将上述所产生的置乱序列与明文信息、前一个加密的密文信息以及与之相对应的上块密文信息相结合来生成密文图像,增加了两过程之间的耦合度,同时保证了相邻像素之间以及各子块之间的相关性,从而能够有效的抵御已知/选择明文等各种攻击。理论分析及实验表明该算法具有密文相关度低,密钥空间更大,安全性高等优点。最后对论文工作进行了全面的总结,并指出了混沌图像加密的进一步研究方向。
[Abstract]:With the rapid development of computer and network technology, the problem of network security has attracted more and more attention. The digital image, because of its image, visual and vivid features, makes it an important expression in the transmission of network information. However, the traditional encryption algorithm, such as AES, is no longer suitable for image encryption because the digital image has the characteristics of large data volume, high redundancy, strong correlation among pixels, and the like. On the other hand, the hybrid system makes it particularly suitable for image encryption because of its sensitivity to the initial conditions and control parameters, the density of the periodic points, and the topological transitivity. In recent years, a large number of hybrid-based image encryption algorithms have been proposed. Most of the traditional encryption techniques are based on one-dimensional mixed encryption. Because these encryption techniques have the disadvantages of small key space, low security, and so on, these encryption algorithms are very defective. In this paper, the fractional-order Chen system and the high-dimensional hybrid system are applied to the image encryption algorithm, and the security and the complexity of the algorithm are improved. The main work and innovation of this paper are: 1. First of all, the present situation and significance of the research on the encryption of the mixed image are analyzed, and the basic knowledge of the theory of mixing and the basic knowledge of cryptography are introduced in detail, and the relation between them is cut. In this paper, the general procedure and the evaluation index of the hybrid image encryption algorithm are introduced. The image encryption based on the fractional-order Chen system is presented in this paper. The method comprises the following steps of: firstly, generating a required scrambling sequence by using a fractional-order Chen system; then, performing selection of a row-and-column scrambling sequence by the judgment of the plaintext information, so as to ensure the correlation with the plaintext; and performing a packet-exclusive-OR algorithm on the scrambled image to carry out the pixel value thereof. preprocessing, carrying out two-wheel pixel encryption on the pre-processed image at the same time, and increasing the complexity of the algorithm and and finally, comparing with an integer-order Chen system algorithm, the algorithm has the advantages of low cipher text degree, larger key space and higher security. 3. Based on the properties of the super-hybrid system, a complete scrambling scheme is proposed. The method comprises the following steps of: firstly, generating the required mixed sequence by using a super-hybrid system, and further realizing the scrambling of the position of the pixel points; and generating an encryption sequence as a key of the logistic mapping by using the generated scrambling sequence as a key of the logistic mapping, and increasing the two processes. and the sum of the gray values of all the pixel points after the single point pixel point and the previous encryption are used to encrypt the pixel value, and the correlation between the pixel value and the clear cipher text is ensured, so that the known/ selected plaintext can be effectively resisted. The theoretical analysis and the experiment show that the algorithm has the advantages of low cipher text correlation, larger key space and security. in ord to improve that security of the algorithm, a block-based method is proposed to improve the security of the algorithm. The method comprises the following steps of: firstly, generating four groups of mixed color sequences by using a high-dimensional hybrid system, and simultaneously dividing the images into four equal-size four, and determining the selection of the scrambling sequence through the plaintext information of each block, and then the generated scrambling sequence is combined with the plaintext information, the previous encrypted ciphertext information and the upper block cipher text information corresponding to the plaintext information to generate the ciphertext image, the coupling degree between the two processes is increased, The correlation between the blocks so that it can be effectively protected against known/ selected The theoretical analysis and the experiment show that the algorithm has the advantages of low cipher text correlation, larger key space, In the end, the paper summarizes the work of the paper, and points out the addition of the mixed image.
【学位授予单位】：扬州大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TP309.7

【共引文献】