【作者】 张莉；

【导师】 张雅彬； 凌林本；

【作者基本信息】 哈尔滨工程大学 ， 电子与通信工程（专业学位）， 2021， 硕士

【摘要】 互联网技术的高速发展让网络信息从隐蔽私密变得公开透明,保证网络信息安全也成为研究的热点问题。图像因其生动形象、信息丰富成为互联网上最常见的信息传递方式,其安全问题自然变得至关重要。现阶段常见的图像加密算法大多为基于空域的图像加密算法,其中基于DNA编码与超混沌系统的图像加密算法虽然具有足够大的密钥空间、较好的安全性能,但是也存在固有缺点:面对选择明文攻击与噪声攻击时表现不佳。基于变换域的图像加密算法虽然抗干扰能力强、加密效率高,但是也存在扩散和置乱效果不理想、传输不便等问题。因此将基于DNA编码与超混沌系统的空域图像加密技术与变换域图像加密技术相结合成为了具有重要意义的研究课题。本文针对目前图像加密算法大多为单一域的对称加密、密钥与原始图像无关、抗选择明文攻击能力较弱等问题,将空域的DNA编码与混沌系统加密操作与变换域的分数傅里叶变换操作相结合,同时引入相位截断操作,提出了基于DNA编码与超混沌的变换域非对称图像加密算法。本文具体研究内容如下:首先,对复合DNA编码与超混沌系统的图像加密技术进行了系统的研究,对目前常用的加密结构进行了计算机仿真,基于仿真结果对该结构进行了详尽分析并指出了其中存在的安全问题。其次,针对前述系统存在的问题,提出了一种基于DNA编码与超混沌的变换域非对称灰度图像加密算法。该算法在空域、频域两个层面进行操作实现图像加密,保证了算法具有足够大的密钥空间,同时能够抵抗常见的攻击;相位截断操作将算法转化成非对称的,进一步提升算法的安全性;引入哈希256算法使其能够根据原始图像产生密钥,实现一次一密。仿真结果证明了该算法的可行性,安全性分析则表明算法对常见的攻击具有极强的鲁棒性。最后,将提出的灰度图像加密算法进行了扩展,使其能够应用于彩色图像加密。针对常见的彩色图像加密算法中三通道分量之间相关性较强的问题,将三通道分量与补充的混沌矩阵合并成一个灰度图像对此进行统一变换,以此破坏加密图像三分量之间的相关性,提升系统的安全性。仿真结果表明提出的算法对彩色图像加密效果极好,安全性分析证明了该算法在抵抗常见攻击时表现优异。更多还原

【Abstract】 The rapid development of Internet technology has changed network information from concealment and privacy to openness and transparency,and ensuring network information security has also become a hot issue of research.Images have become the most common method of information transmission on the Internet because of their vivid images and rich information,and their security issues have naturally become crucial.Most of the common image encryption algorithms at this stage are image encryption algorithms based on the space domain.Although image encryption algorithms based on DNA encoding and hyperchaotic systems have a large enough key space and good security performance,they also have inherent shortcomings:It performs poorly when selecting plaintext attacks and noise attacks.Although the image encryption algorithm based on the transform domain has strong anti-interference ability and high encryption efficiency,it also has problems such as unsatisfactory diffusion and scrambling effects and inconvenient transmission.Therefore,the combination of spatial image encryption technology based on DNA coding and hyperchaotic system and transform domain image encryption technology has become an important research topic.In this paper,the current image encryption algorithms are mostly single-domain symmetric encryption,the key has nothing to do with the original image,and the ability to resist selected plaintext attacks is weak.The spatial domain DNA encoding and chaotic system encryption operations are combined with the fractional Fourier transform in the transform domain.Combining operations and introducing phase truncation operation,a transform domain asymmetric image encryption algorithm based on DNA coding and hyperchaos is proposed.The specific research content of this paper is as follows:Firstly,the image encryption technology of compound DNA coding and hyperchaotic system is studied systematically.The encryption structure of DNA coding and hyperchaotic system is simulated by computer.Based on the simulation results,the structure is analyzed in detail and the existing security problems are pointed out.Secondly,aiming at the security problems of the above system,a transform domain asymmetric gray image encryption algorithm based on DNA coding and hyperchaos is proposed.The algorithm operates in the spatial domain and frequency domain to realize image encryption,which ensures that the algorithm has enough key space and can resist common attacks such as selective plaintext attack;the phase truncation operation transforms the algorithm into asymmetric,which further improves the security of the encryption algorithm;the hash 256 algorithm is introduced to generate the key according to the original image to realize one-time encryption.Computer simulation shows that the encryption algorithm has good security and resistance to different attacks.Finally,the proposed gray-scale image encryption algorithm is extended to make it applicable to color image encryption.Aiming at the problem of low correlation between the three-channel components common in color image encryption algorithms,the three-channel component and the complementary chaotic matrix are combined into a gray image,which enhances the correlation between the three-channel components of the encrypted image and improves the system Security.Computer simulation shows that the encryption algorithm can realize the encryption of color images very well,and has shown excellent performance in key space,key sensitivity,and anti-attack ability.更多还原