【作者】 罗维潮；

【导师】 付永庆；

【作者基本信息】 哈尔滨工程大学 ， 通信与信息系统， 2007， 硕士

【摘要】 近年来，随着宽带网的发展，图像数据在网上越来越流行。可是，网络上的一些图像数据是要求保密通信的，为了保护他们不被窃取，就需要加密图像数据。本文简要介绍了数字图像加密技术的意义、研究现状及发展趋势，探讨了数字图像加密和密码学的基本原理。根据混沌系统具有伪随机性、确定性和对初始条件与系统参数的极端敏感的特性，提出了将二维logistic混沌映射与数字图像加密技术相结合，可以构造出非常好的图像信息加密系统。本文研究了二维Logistic混沌映射的性质，提出了一种二维logistic混沌序列的生成方法，然后讨论用其对图像离散小波变换后系数矩阵进行调整和置乱处理问题。组织了加密图像的破解实验、抗干扰实验和聚类压缩后加密实验。实验结果表明该混沌序列加解密算法，扩展了密文空间，密文分布均匀，能够克服低维混沌动力学系统易受攻击的缺点。具有密图文件保密性高，密钥简单，重构图像与原图像一致性良好等特点。而且本算法能够经受住传输过程中噪声的影响。结合模糊聚类压缩算法加密压缩后的图像效果良好，且大大减少了图像数据的传输量。更多还原

【Abstract】 With the development of the broad band,image data is more and more popular on the internet recently. But some image datas of internet request secrecy communications. For protecting them from eavesdropper, we need to encrypt important image data.In this paper, the significance ,present state and perspectives of image encryption is represented simply, and we discuss the essential theory of digital image encryption and cryptography. Based on chaotic systems with good properties such as pseudorandom,determinacy and sensitive dependence on their initial condition and system parameter, chaotic theory and digital image encryption are combined, which can design the better system of image encryption. In this paper, the character of two-dimensin logistic map is studied, present a kind of the generating method of two-dimension logistic chaotic sequences. And then the problem of adjusting and scrambling the discrete wavelet transform coefficient matrix of an image using this chaotic sequence is presented. We organize the attack experiments anti-disturb experiments, cryptography experiments after clustering compression experiments. Concluding from experiments prove that the method expanded the cryptograph space, the property of cryptograph is uniform distribution. The algorithm overcomes low dimensional chaotic prone to be defected. The encryption method has advantages in high secrecy, simple secret key and good identity between the original image and the restored image. Moreover, during the transmission ,the algorithm can go through the effects of noise. Combined with clustering compression algorithm, encrypt the compression image ,the result is better,and this has greatly reduce the transmission of image data.更多还原