基于离散混沌CAT的图像加密算法研究与实现

针对图像加密算法中迭代性高、低维离散混沌加密密钥空间小、保密性低等特点,提出利用CAT映射对图像进行离散化,利用该映射的周期性变化对图像进行加密,对不同大小的图像采用不同的周期进行加密.通过实验表明:加密算法能对图像进行有效的加密,得出最佳的参数以达到最好的图像加密效果.     

超混沌图像加密方案的分析与改进

根据选择明文攻击原理,对一种超混沌图像加密算法进行了分析,结果表明该算法不能抵抗选择明文攻击。提出了一种改进的超混沌图像加密算法;对改进算法进行了安全性分析和实验测试。理论分析及实验结果表明,改进算法克服了原算法不能抵御选择明文攻击的缺陷,而且能拥有更好的统计特性、差分特性等密码学特性和更高的加密速度。     

Performance evaluation of P2P-TV diffusion algorithms under realistic settings

Internet video and peer-to-peer television (P2P-TV) are attracting more and more users: chances are that P2P-TV is going to be the next Internet killer application. In recent years, valuable effort has been devoted to the problems of chunk-scheduling and overlay management in P2P-TV systems. However, many interesting P2P-TV proposals have been evaluated either in rather idealistic environments, or in the wild Internet. Our work sits in between these two antipodean approaches: our aim is to compare existing systems in a controlled way, but taking special care in realistic conditions for their evaluation at the same time. We carry on a simulation analysis that considers several factors, modeling the L7 overlay (e.g., chunk scheduling, topology management, overlay topology, etc.), the L3 network (e.g., end-to-end latency models, fixed vs dynamic conditions, etc.), and the interaction of both layers (e.g., measurement errors, loss of signaling messages, etc.). To depict a comprenshive system view, results are expressed in terms of both user-centric and network-centric metrics. In a nuthshell, our main finding is that P2P-TV systems are generally robust against measurement errors (e.g., propagation delay or capacity estimation), but are on the contrary deeply affected by signaling errors (e.g., loss or outdated system view), which are often overlooked without justification.     

Assessment of diverse image encryption mechanisms under prevalent invasion

Multimedia Tools and Applications - Image encryption mechanisms provide confidentiality and concealment of information (image) in transmission over the alleyway, susceptible to prevalent invasions....     

Gauss-Markov加密矩阵构造及图像加密应用

为了解决加密矩阵难以构造的问题,提出一种获得整数矩阵的新算法,利用Gauss-Markov过程生成一个随机序列,将该序列转换为一系列的低阶整数矩阵,从中寻找行列式等于l的整数矩阵,并对这些矩阵进行张量积运算得到高阶加密矩阵,应用于数字图像加密.加密实例和理论分析及对比表明,该算法可自动生成安全性很高的加密矩阵,且加密结果具有良好的随机特性和自相关性,能满足密码学的要求.     

Analysis and implementation of no-equilibrium chaotic system with application in image encryption

Applied Intelligence - The study of no-equilibrium chaotic system is one of the recent hot topics. This paper constructs a new no-equilibrium chaotic system by introducing an additional variable...     

GPU加速希尔加解密方法的研究

GPU有效地利用了数量巨大的晶体管制造大量的处理单元,适用于处理单任务多数据（SIMD）的计算任务。研究了GPU的体系结构及CUDA的编程模式,改进了基于CPU的希尔加解密方法,使用多个线程将计算中耗时的矩阵相乘部分改造成SIMD模式,并分析了线程块内线程数对加速比的影响。实验结果表明,基于GPU的并行矩阵相乘的希尔加解密方法成功实现了硬件加速,相对于CPU上运行的希尔加解密方法,其执行效率明显提高,可获取12倍以上的加速,并易于扩展,对大规模数据加密和解密处理呈现出高效的处理能力。     

Optimisation of control parameters for genetic algorithms to test computer networks under realistic traffic loads

Although many studies have focused on testing computer networks under realistic traffic loads by means of genetic algorithms (GAs), little attention has been paid to optimising the parameters of the GAs in this problem. The objective of this work is to design and validate a system that, given some constraints on traffic bandwidth, generates the worst-case traffic for a given computer network and finds the traffic configuration (critical background traffic) that minimises throughput in that computer network. The proposed system is based on a meta-GA, which is combined with an adaptation strategy that finds the optimum values for the GA control parameters and adjusts them to improve the GA's performance. To validate the approach, different comparisons are performed with the goal of assessing the acceptable optimisation power of the proposed system. Moreover, a statistical analysis was conducted to ascertain whether differences between the proposed system and other algorithms are significant. The results demonstrate the effectiveness of the system and prove that, when the background traffic is driven by a GA that uses the parameters obtained from the system, the computer network's performance is much lower than when the traffic is generated by Poisson statistical processes or by other algorithms. This system has identified the worst traffic pattern for the protocol under analysis.     

面向嵌入式应用的加密算法开销与性能分析

为了找出最适合无线传感器网络应用的加密算法,通过对SEA算法、PRESENT算法、HIGHT算法进行理论分析,利用Atmega128L微处理器作为评估平台,对其开销和性能做了估计,并将仿真结果与其它算法进行比较.实验结果表明,HIGHT具有最优的性能,并且其内存开销也比较小,非常适合用于资源受限的应用中.为了高效地实现一种加密算法,其计算字长必须接近微处理器的字长.此外,SEA和PRESENT并不适合软件实现,硬件实现是更好的选择.     

基于小波变换域混沌加密与循环移位的改进图像加密算法*

传统混沌图像加密算法均对图像的空间域进行处理,该情况的秘钥敏感度较低,关联性较高,对此,提出一种基于小波变换域混沌加密与循环移位的改进图像加密算法。首先,根据原图像生成对应的秘钥,并采用该秘钥对原图像作循环移位处理;然后,将图像进行小波变换,获得小波变换域;最终,对图像进行二维混沌映射,作置乱处理。实验结果表明,本算法的统计性能、鲁棒性能以及秘钥敏感性均具有一定的优势。     

基于混沌的图像复合置乱和多级信息隐藏算法

提出一种基于混沌映射和灰度替换的图像复合置乱算法,算法采用了一维logistic混沌序列对图像的行列分别置乱,并与灰度替换相结合,实验表明其具有较高的安全性。利用人眼视觉系统（HVS）的特性,提出一种新的基于DCT的信息隐藏算法,通过选取频域变换后的适当系数,调整其尾数的奇偶,达到嵌入秘密信息的目的,并将其扩展为基于其他变换域的多级信息隐藏技术,实验证明其具有隐藏量大、鲁棒性较强、盲提取的优点。     

基于混沌和细胞自动机的图像加密算法

为了设计加密性能好、容易实现的加密系统,充分利用混沌系统的密码学特性和细胞自动机良好的加密性能,提出了一种基于混沌系统和触发细胞自动机的图像加密算法.算法先利用混沌序列对图像进行加密处理;通过构造反转规则建立触发细胞自动机,并根据触发细胞自动机的迭代规则对图像进行二次加密.加密过程简单高效,且具有较大的密钥空间,可以保证系统的安全性.实验结果表明,该算法具有较好的加解密性能,且较小的邻域半径即可得到良好的加密效果,因此非常便于硬件实现.     

Lightweight,dynamic and efficient image encryption scheme

Multimedia Tools and Applications - Recently, there has been a growing attention for Chaos-based image encryption algorithms. This class of algorithms relies on embedded chaotic maps to ensure a...     

有源磁控忆阻超混沌电路实现及图像加密

在一个广义三阶Rucklidge系统的基础上提出基于二次非线性有源磁控忆阻器的四阶超混沌电路系统。对该系统的动力学行为进行理论分析和数值仿真,系统相图、Lyapunov指数谱、分岔图和共存吸引子均表明该系统具有丰富的动力学行为和新的拓扑结构。并利用Multisim电路仿真软件和FPGA数字硬件电路设计实现了该系统的电路,实验结果与数值仿真结果一致。最后将置乱-扩散算法与DNA加密相结合设计了一种图像加密算法,利用新系统混沌序列对图像进行加密,并对加密后的图像进行了加密直方图、相邻像素相关性、敏感性、鲁棒性和信息熵等分析。结果表明,新系统对混沌密钥及明文都非常敏感,密钥空间较大,提出的混沌系统应用于图像加密具有较高的安全性能。     

一类方程的混沌反控制及在图像加密中的应用

为了研究一类方程的混沌反控制及其在图像加密中的应用问题,提出了基于延迟时间状态反馈控制的方法.设计了一个延迟反馈控制器,使得受控系统产生混沌行为,并用数据仿真给出了受控系统具有混沌特性的部分指标;同时根据小波变换,结合受控的混沌系统提出了一种图像加密方案.实验结果表明,该方案不但拥有较大的密钥空间,而且对密钥和明文相当敏感,具有优良的扩散性和扰乱性能,并能抵抗各种攻击.     

基于位平面的LSB图像隐藏算法分析及改进

介绍图像信息隐藏技术中基于空间域方法中位平面的思想,分析了传统的最低有效位(LSB)隐藏算法以及在此基础上改进的奇偶标识位隐藏算法,提出了一种失真度更低、安全性更高的新隐藏方法——索引数据链隐藏算法。实验证明,采用该方法对载体数据的改变量要少于常规方法,可以有效地提高隐藏信息的安全性。     

图像复原的算法研究

近年来有关图像复原的研究成果大量涌现，焦点大多集中在图像中的纹理合成或面向结构的图像润饰。分析的几个重要算法，即基于同步的结构纹理填充算法、基于统计的图像润饰算法和基于样本的图像润饰算法，突破了以往研究的局限性，取得了较好的复原效果。基于同步的结构纹理填充算法，首先将纹理合成和图像润饰技术同时应用于图像恢复，基于统计的图像润饰算法则全面利用了图像的全局信息，基于样本的图像润饰算法则将纹理合成和图像润饰技术的特性融于一体。对此进行了分析探讨，并在此基础上总结了目前图像复原研究状况。     

基于感知器模型的混沌图像加密算法

提出了基于感知器模型的高维混沌加密系统,描述了高维的Lorenz混沌系统和神经网络中感知器模型,利用高维混沌映射生成的伪随机序列,动态的调整单层感知器中各个神经元的权重,从而实现了混沌图像将加密,并对算法进行数字仿真和安全性分析.理论分析和实验结果表明,该算法具有较高的安全性,对已有的攻击方法有较强的抵抗能力.     

一种混合型混沌图像加密算法的设计

本文设计了一种结合Cat和Logistic映射的混合型混沌加密算法。首先文章给出了该图像加解密的算法流程,在置乱变换和扩散变换主要算法程序的基础上,对实验结果从密钥空间、图像的直方图、图像的相关性、图像的信息熵等方面进行了分析,证明该算法对图像信息加解密具有良好的效果。     

Chaos-based image encryption scheme combining DNA coding and entropy

Information security has became more and more important issue in modern society, one of which is the digital image protection. In this paper, a secure image encryption scheme based on logistic and spatiotemporal chaotic systems is proposed. The extreme sensitivity of chaotic system can greatly increase the complexity of the proposed scheme. Further more, the scheme also takes advantage of DNA coding and eight DNA coding rules are mixed to enhance the efficiency of image confusion and diffusion. To resist the chosen-plaintext attack, information entropy of DNA coded image is modulated as the parameter of spatiotemporal chaotic system, which can also guarantee the sensitivity of plain image in the encryption process. So even a slight change in plain image can cause the complete change in cipher image. The experimental analysis shows that it can resistant different attacks, such as the brute-force attack, statistical attack and differential attack. What’s more, The image encryption scheme can be easily implemented by software and is promising in practical application.