【作者】 茅耀斌；

【导师】 王执铨；

【作者基本信息】 南京理工大学 ， 控制科学与工程， 2003， 博士

【摘要】 随着网络技术和数字信号处理技术的发展与流行，多媒体信息安全显得日益重要。由于多媒体数据本身具有高冗余性、数据量大等特点，因此对它的安全保护有着特殊要求，譬如：要求加密算法具有快速性和低计算强度；要求多媒体信息能做到自认证；以及对数据的安全保护不能影响其可用性等。从这些方面来说，传统密码学对多媒体数据的保护不是十分有效。 考虑到传统密码学的不足，近年来，人们开始寻求多媒体信息保护的新方法。这其中，基于混沌的加密技术和数字水印技术显示出了其独到的优势，有可能成为新的多媒体保护的有效手段。 本论文重点研究了图像数据安全，主要成果包括： (1)从混沌映射的特性出发，研究了密码变换与混沌映射的关系。研究了用于图像加密的混沌分组密码的设计方法，构造了利用高维可逆混沌映射进行图像加密的方法，提出了利用二维混沌cat映射对图像进行加密的方法，并将二维可逆混沌映射扩展到了三维，提出一种基于三维Baker映射的图像加密方案，该方案在图像加密速度和安全性上都有显著的提高； (2)对混沌伪随机二值序列、一般混沌伪随机数序列的产生方法进行了研究，介绍了两类混沌伪随机二值序列产生方法，并对利用其中一种方法产生的混沌伪随机二值序列的性质进行了研究。研究了混沌伪随机数的数字实现问题，并利用混沌反馈移位寄存器法设计了一种适合于集成到数字芯片中的混沌流密码算法。结合图像小波编码算法，提出了一种结合SPIHT小波图像编码的混沌图像加密方法。该算法很好地和小波图像编码集成到了一起，在压缩域内进行数据加密，并且能够保留原来图像编码的数据渐进传输特性，是一种有应用前景的图像加密方法； (3)针对图像水印的不可见性要求，研究了人眼视觉特性，提出了三种基于视觉特性的水印算法，分别为：利用图像Gaussian分解的基于离散高斯变换(DGT)的水印算法、结合视觉对比度敏感性矩阵的离散余弦变换(DCT)水印以及利用图像融合技术的基于HVS的离散小波变换(DWT)水印。实摘要博士学位论文 验表明，采用人眼视觉特性的图像水印能够显著减小图像视觉降质，提高 水印的鲁棒性;(4)将混沌与水印技术结合是水印研究的一个新方向，本文在这个方面也作了 有益的尝试，提出了一种结合二维Baker映射的混沌半易损水印算法。该 算法在存在图像噪声和经受中度JPEG压缩的情况下，能够很好地判断出 图像是否受到篡改，并检测出图像受到篡改的部位。 最后论文分析了当前在混沌加密与图像水印研究中存在的问题，并指出了进一步的研究方向。更多还原

【Abstract】 The advance of digital signal processing and the prevalence of network communication make the protection of multimedia content become a crucial issue in information security that attracted much attention of both the government and the public. Due to the intrinsic properties of multimedia such as high redundancy and bulk capacity, special concerns have to be made, which includes speediness of operation, low computational overload, self-authentication of the data and noninterference of the availability of data. All these matters have risen up a great puzzle in multimedia protection, which current cryptology feels difficult to deal with.In consideration of the deficiency of traditional cryptology, recently people are seeking more effective approaches to fulfill the requirements of multimedia protection, among which chaos based encryption and digital watermarking technology exhibit prospective superiority.In this dissertation, some issues in image security are studied and several chaos based encryption schemes and image watermarking algorithms are composed as well, which are detailed as follows:(1) Relationship between cryptological transformation and chaotic map is investigated in terms of chaotic properties and methodology on design of chaotic block cipher for image encryption is provided. Concerning with image encryption, several encryption schemes based on high dimensional reversible chaotic map are put forth such as one based on cat map or Baker map. To fasten operation speed and enhance encryption security, a novel image encryption scheme based on three dimensional Baker map that extended from its two dimensional counterpart is brought out. The significant performance improvement is proved by cryptanalysis and experiments.(2) Universal approaches to generating chaotic pseudo-random sequence, especially to chaotic pseudo-random bit sequence (CPRBS), are studied and two CPRBS generation algorithms are investigated in detail. Properties of the CPRBS generated by one of the two algorithms are further explored. Then, to solve the degradationcaused by digitization that unavoidable in practical realization, a chaotic stream cipher taking use of chaotic feedback shift registers is brought out, which has been shaped to be implemented in digital chip. Finally an image encryption method jointly using SPIHT wavelet compression and chaos is proposed. The dual merits that either being able to perform encryption on compressed data stream or not losing the progressive data transmission property that inherently possessed by original SPIHT coding makes the method a promising encryption scheme for practical use.(3) To meet the requirement of invisibility of image watermarking, human visual properties have been investigated in the thesis. Three kinds of robust perceptual watermarking techniques that take use of Discrete Gaussion Transform (DGT), Discrete Wavelet Transform (DWT) accompanied with image fusion and Discrete Cosine Transform (DCT) combined with visual contrast sensitivity function respectively also have been proposed. Empirical study shows that HVS based watermarking schemes can significantly increase the robustness of watermark while reduce image quality degradation.(4) As chaos based watermarking has emerged as a new research direction, efforts on composition of chaotic watermark have also been made by putting forward a semi-fragile watermarking scheme that incorporated with two dimensional Baker map for authentication purpose. The algorithm can not only judge image tamper but also find out the tamper location in image even in face of noise addition and mild JPEG compression.Finally, the thesis is concluded by pointing out some open issues on the research of chaos based encryption and image watermarking as well as highlight some further research directions.更多还原