【作者】 赖师悦；

【导师】 廖晓峰；

【作者基本信息】 重庆大学 ， 计算机系统结构， 2010， 硕士

【摘要】 随着计算机处理能力和网络技术的不断发展,多媒体已广泛地运用到了社会生活的各个领域。同时,多媒体通信的安全问题也日益突出。密码学是解决这一问题的重要技术。与文本数据不同,多媒体具有数据量非常大的特点,对其加密会消耗大量的计算资源和时间。数字图像是多媒体的一种,其研究成果易于推广到其它多媒体形式中。本文主要研究在空域上设计出一种安全、高效的数字图像加密算法。论文的工作主要包括以下几个方面:①简要介绍空域图像加密的基础,包括密码学基础、图像加密的思想、性能指标、扩散技术以及并行图像加密的基本要求。②分析和总结现有的典型空域图像加密算法的特点,指出其优点与不足以及不足之处的根源。③提出了波传播加密的思想,即通过模拟离散化后的物理波在图像上传播对图像进行加密。论文给出了其实现细节,对其进行了全面分析,总结出该加密思想的优点与不足。并指出了弥补其不足的方法。④根据波传播加密思想的特点,将其与自适应加密相结合,提出了自适应波传播加密算法。该法首先将图像进行分块,从部分块中提取特定信息,将其与密钥一起用来控制波的三个参数构造四条正弦波。然后利用所构造的正弦波对未提供特定信息的图像块进行加密,最后用同样的方法利用已加密的块对未加密的块进行加密。论文给出了详细的加密和解密过程,提出了将加密过程并行化的框架以及将其扩展到彩色图像加密的方法,并通过仿真实验、与两个典型空域图像加密算法的对比以及对实验结果的分析证明了自适应波传播加密算法在敏感性、速度和安全性上的高性能。最后是全文的总结,并提出了论文的不足以及今后进一步研究改进的方向。更多还原

【Abstract】 With the development of computing and network technology, multimedia data are used more and more widely. So,the security of multimedia data draws increasingly attention. Cryptography is the major method to resolve it. However,contrast to texts, multimedia contents contain huge volume of data, which makes their encryption become very slow and power-consuming. This paper focuses on the approaches to design a secure and fast algorithm for image in spatial domain. Some of the conclusions and contribution of this paper are listed as follows.①A brief description of the basic theory for image encryption in spatial domain is presented,including basic theory of cryptology, basic ideas of image encryption, performance indexes, diffusion techniques and basic requirement of parallel image encryption.②Analysis and summarization of the existing classical image encryption in spatial domain. Point out its features, advantages, disadvantages as well as where its weakness lies in.③Put up with the idea of wave transmission, that is, encrypting a image by simulating the transmission of discrete waves on it. Provide the details of realizing it. Carry out a thorough analysis on it to find its advantages,disadvantages and the way to make up with its weakness.④By combining the idea of wave transmission with self-adaptive encryption according to its feature,the image encryption algorithm based on self-adaptive wave transmission is proposed. The algorithm first extracts some certain information from a part of the image after doing partitioning; combine them with keys to control the three parameters of four sin waves. Then, using the four waves to encrypt the left part from which none information is extracted. At last, the unencrypted part is encrypted with the encrypted part using the same method. The detailed encryption and decryption progress as well as its parallelized frame are given. Simulation results for a gray-level and a color image and comparison with other typical algorithms have demonstrated the high performance on the sensitivity, speed, and security of the proposed algorithm.Finally, there comes the conclusion of this dissertation. Some disadvantages and further work are also given.更多还原