Image encryption using the random FrDCT and the chaos-based game of life

A novel image encryption algorithm using the random fractional DCT (RFrDCT) and the chaos-based Game of Life (GoL) is presented here. Firstly the plaintext image is transformed by the reality-preserving RFrDCT into the RFrDCT domain, and a preliminary encryption output is obtained. And then a combination of the confusion and diffusion (C&D) processes is performed in the transform domain, where the confusion process is carried out by GoL, and the diffusion process is carried out by an XOR operation. Therefore a more random-like encryption result can be obtained after further encryption by the C&D. Both the GoL and XOR operation are based on chaos whose control parameters serve as cipher keys in order to enlarge cipher space and enhance key sensitivity. Theoretical analysis and simulation experiments for the proposed algorithm are described, the desirable encryption performance is obtained, and it is secure against various common attacks.     

一个具有多翼吸引子的四维多稳态超混沌系统

构造了一个只有一个平衡点的四维超混沌系统,此系统表现出丰富的多稳态特性,亦具有多翼吸引子。数值分析了系统的动力学特性,仿真了系统的模拟电路和数字电路,探讨了系统的动态复杂度,测试了系统超混沌序列的随机性。分析结果表明,在多组参数值下,系统均存在不同类型的吸引子共存,譬如:两个周期吸引共存,周期与拟周期吸引子共存,双翼混沌与超混沌吸引子共存,两个双翼混沌吸引子共存,双翼与四翼混沌吸引子共存,两个双翼超混沌吸引子共存,两个双翼拟周期吸引子共存,两个双翼超混沌、四翼混沌、四翼超混沌等四个吸引子共存。系统的数字电路和模拟电路的仿真结果均与数值分析结果一致,表明了系统的可实现性。另外,在混沌和超混沌状态下系统复杂度高,且超混沌序列通过了SP800-22 Revla的15项随机测试。     

离散余弦变换域内的Retinex图像增强模型研究

针对现有离散余弦变换（DCT）域图像增强算法大多统一处理DCT系数,且不能有效抑制块状效应的问题,将Retinex思想引入DCT域,提出一种新增强算法：将DCT系数分为入射分量和反射分量,构造一种带强光抑制的函数,将入射分量映射到理想的动态范围;定义一种频带限制的对比度,实现反射分量的局部细节增强;使用子块分解方法抑制块状效应。实验结果表明,与现有Retinex及DCT域增强算法相比,该算法具有更好的细节增强及强光抑制效果,且能较好抑制块状效应。     

一种基于人眼感知特性的彩色图像压缩算法

目的研究结合人眼感知特性的彩色图像压缩技术。方法结合人眼对比度敏感视觉特性及其数学模型,基于彩色图像频谱特征,提出一种适合于彩色图像的压缩算法方案,并对图像进行3种压缩比的压缩仿真实验。结果提出的压缩算法方案在完全不影响人眼观察的情况下压缩比可达15∶1,压缩比达到64.1538∶1时,解压缩图像仍能在一定的误差范围内达到较好的视觉效果,且PSNR仍能达到30 dB以上。结论提出的压缩算法方案在保证图像压缩质量的前提下能够实现较高的压缩比,完全可以满足实际生活中彩色图像存储和传输的需要。     

一种基于小波变换的遥感图像压缩算法

为验证图像压缩算法122.0-B-0对遥感图像的有效性,在对该算法进行了较为详细的研究后,对该算法进行了软件实现,然后将该算法与JPEG2000、SPIHT算法在压缩效率及压缩速度上进行了比较.实验结果表明:该算法在较低码率下压缩性能与JPEG2000、SPIHT算法相当,在较高码率下压缩性能略微下降,但在相同码率下它的编码速度比JPEG2000快2倍左右,比SPIHT算法约快1.5倍左右,且编解码速度与码率成正比.该算法采用的编码方式相对简单,无反馈操作,可适应于不同内存大小的压缩系统,并采用分段编码有效地防止误码扩散,因此在空间飞行器上具有巨大的应用价值.     

Optical image encryption scheme with multiple light paths based on compressive ghost imaging

An optical image encryption method with multiple light paths is proposed based on compressive ghost imaging. In the encryption process, M random phase-only masks (POMs) are generated by means of logistic map algorithm, and these masks are then uploaded to the spatial light modulator (SLM). The collimated laser light is divided into several beams by beam splitters as it passes through the SLM, and the light beams illuminate the secret images, which are converted into sparse images by discrete wavelet transform beforehand. Thus, the secret images are simultaneously encrypted into intensity vectors by ghost imaging. The distances between the SLM and secret images vary and can be used as the main keys with original POM and the logistic map algorithm coefficient in the decryption process. In the proposed method, the storage space can be significantly decreased and the security of the system can be improved. The feasibility, security and robustness of the method are further analysed through computer simulations.     

QR code-based non-linear image encryption using Shearlet transform and spiral phase transform

In this paper, we propose a new quick response (QR) code-based non-linear technique for image encryption using Shearlet transform (ST) and spiral phase transform. The input image is first converted into a QR code and then scrambled using the Arnold transform. The scrambled image is then decomposed into five coefficients using the ST and the first Shearlet coefficient, C₁ is interchanged with a security key before performing the inverse ST. The output after inverse ST is then modulated with a random phase mask and further spiral phase transformed to get the final encrypted image. The first coefficient, C₁ is used as a private key for decryption. The sensitivity of the security keys is analysed in terms of correlation coefficient and peak signal-to noise ratio. The robustness of the scheme is also checked against various attacks such as noise, occlusion and special attacks. Numerical simulation results are shown in support of the proposed technique and an optoelectronic set-up for encryption is also proposed.     

基于人眼视觉特性的印刷图像压缩技术研究

利用人眼对比度感知特性,计算了包装印刷图像的最小感知觉察误差阈值,通过阈值对图像的DCT变换系数进行量化,再采用Huffman编码方法实现编码,并通过实验验证。实验获得其峰值信噪比为49.647 1dB,压缩比达到11.497 7,编码效率达到0.743 8,即从客观评价上衡量数据压缩性能的指标均达到了较好的效果,证明了解码图像与原始图像间的差异较小,且从主观上人眼几乎不能分辨其差异,说明图像使用的压缩技术不会对图像的品质产生影响。该压缩算法既能达到一定的压缩效果,又能不影响包装印刷图像的观测效果,所以能够较好地满足包装印刷图像传输的要求。     

基于提升方案与SPIHT的无失真图像压缩

基于提升方案的整数Deslauriers-Dubuc（6,2）可逆双正交小波变换,可由加法和移位完成,便于硬件实现。与SPIHT和熵编码结合可实现无失真图像压缩。与ARJ,JPEG,整数Haar变换结合DPCM以及分块DPCM中的无失真压缩方法相比,压缩比分别平均提高了50％,35％,20％,2％左右。     

Modelling of dynamical system and generalised circulant matrix in image encryption

Abstract

In this paper, a modelled image encryption scheme is presented, of which generalised circulant matrix is employed together with dynamical chaotic system. The strong correlations among adjacent pixels in plain-image can be declined greatly by the proposed scheme. Meanwhile, the diffusion transform is considered simultaneously to avoid statistical analysis, known plaintext and chosen plaintext attack. The experimental results show that the proposed scheme can suggest an efficient way to hide the image information, and has the advantages of large key space, sensitive to initial conditions and zero correlation between adjacent pixels in cipher-image. Moreover, the grey values in the cipher-image are distributed symmetrically. The proposed image scheme can be applied to practical image information transmission and protection in the public.     

提升方案结合改进SPIHT的快速图像压缩方法

针对传统小波变换过程复杂的缺点和 SPIHT 算法编码过程重复运算、存储量大的问题,提出了基于提升方案快速 SPIHT 的压缩方法。该方法采用提升方案弥补传统小波变换的不足,提高了图像的重构质量和小波变换速度,并引入“最小阈值”、“最小输出位”和“最大值表”的思想对SPIHT 算法加以改进,降低了编解码过程的运算复杂度和时间消耗。实验证明,该算法较传统方法编解码速度提高了2.5倍,重构图像的峰值信噪比亦有所提高,是一种有效的快速图像压缩方法。     

Image encryption combining multiple generating sequences controlled fractional DCT with dependent scrambling and diffusion

Based on the fractional discrete cosine transform with multiple generating sequences (MGSFrDCT) and the dependent scrambling and diffusion (DSD), an image encryption algorithm is proposed, in which the multiple-generating sequences greatly enlarge the key space of the encryption system. The real-valued output of MGSFrDCT is beneficial to storage, display and transmission of the cipher-text. During the stage of confusion and diffusion, the locations and values of all MGSFrDCT transformed coefficients change due to DSD, and the initial values and fractional orders of encryption system depend not only on the cipher keys but also on the plain-image due to introduction of a disturbance factor, which allows the encryption system to resist the known-plaintext and chosen-plaintext attacks. Experimental results demonstrate that the proposed encryption algorithm is feasible, effective and secure and able to resist common classical attacks.     

一种基于YC-rC-b颜色空间和视觉特性的彩色图像水印技术

根据图像离散余弦变换频谱图特征及结合人眼对亮度和颜色的对比度敏感视觉特性,提出了一种人眼感知图像最小误差即JND阈值的计算方法,通过计算出的JND阈值,提出了一种基于YCrCb颜色空间的彩色图像水印技术方案。方案依据JND阈值筛选彩色图像的3个分量亮度图变换域频谱系数来进行水印的嵌入和提取。从水印技术方案上看,JND阈值的引入使得水印的嵌入达到最大;嵌入算法使得水印嵌入的位置具有随机性,有力地保证了水印信息的安全性。仿真实验和攻击测试表明:含水印图经压缩攻击后的图像与原始图像基本一样,提取的水印信息与原始水印基本相同;攻击后的含水印图具有较好的透明性和较高的鲁棒性。提出的基于YCrCb颜色空间和人眼视觉特性的彩色图像水印技术方案,是一种可行的、较好的彩色图像技术。     

一种新的基于可逆矩阵的具有完整性检验能力的图像加密方案

为了保护图像信息的安全,论文利用组合理论知识,提出一种新的基于可逆整数矩阵的、具有完整性检验能力的图像加密方案。应用该方案将一个灰度图像加密生成一个脆弱的噪声密图,解密过程是加密的简单逆过程。密图的完整性可以凭借人类视觉系统进行检验,不需要任何复杂的计算。当密图遭受恶意篡改时,解密得到一个噪声图,无法得到原始图像的任何信息。论文加密方案的密钥简单,且密钥空间足够大。理论分析和实验结果证明了,该方案为图像加密提供了一种高安全性和有效的机制。     

Novel bilateral-diffusion image encryption algorithm with compound chaos and LFSR

Abstract

In order to solve the problem of short cycle and low precision of one-dimensional (1D) chaotic function, the new compound two-dimensional chaotic function is presented by exploiting two 1D chaotic functions which are switched randomly. A new chaotic sequence generator is designed by the compound chaos and linear feedback shift register (LFSR). The random properties of compound chaotic functions and LFSR are also proved rigorously. The novel bilateral-diffusion image encryption algorithm and permutation algorithm are proposed based on the compound chaotic function and LFSR, which can produce more avalanche effect and larger key space. The entropy analysis, differential analysis, statistical analysis, cipher random analysis and cipher sensitivity analysis are introduced to test the security of new scheme. The results show that the novel image encryption method passes SP 800-22 standard tests and solves the problem of short cycle and low precision of 1D chaotic function.     

具有hook机制的过滤驱动加解密模型

研究了文件保护的加解密技术。针对文件采用过滤驱动模型进行加解密导致文件标识不统一与内存明文泄露风险增加等安全问题,设计了一种hook机制和过滤驱动方法相结合的加解密模型。该模型采用过滤驱动方法对文件进行加解密,同时引入hook机制对内存中文件操作行为进行捕获,使得加解密前后的文件具有相同标识,在保证用户原有文件操作习惯的同时,实现了文件内存明文恢复风险的降低。理论分析和试验结果表明,该模型在三种加密模式下,可以针对不同文件进行快速加解密,同时较过滤驱动加解密模型,其恢复风险下降3%以上。     

运用PKS系统实现空压机控制的方案

简介PKS系统的控制功能，详细介绍了运用PKS系统对空压机实施控制的方案和内容，经实际运行，控制方案有效、可靠。     

运用PKS系统实现空压机控制的方案

简介PKS系统的控制功能,详细介绍了运用PKS系统对空压机实施控制的方案和内容,经实际运行,控制方案有效、可靠。