基于柱面衍射和彩色空间转换的单通道彩色图像加密

为了解决传统密码系统由于对称特性导致的安全性低的问题,提出了一种新的基于柱面衍射和彩色空间转换的单通道彩色图像加密方法。在加密过程中,首先将彩色图像变换为YCbCr4:2:0格式的单通道图像,然后经过两次柱面衍射和相位截断操作对图像进行加密。在解密过程中,将密钥与密文结合,经过两次柱面逆衍射后重建出彩色原图。由于柱面衍射过程是一个非对称的过程,此算法可以克服基于平面衍射的加密系统的对称特性,将其应用到基于相位截断的加密系统中可以进一步有效提高加密系统的安全性。仿真结果表明,该算法能够有效地对彩色图像进行单通道加密,不仅可以高质量地恢复原始彩色图像,而且加密系统具有较高的安全性。     

三维彩色图像加密的改进与实现

针对三维空间上的彩色图像进行加密处理具有运算量和空间需求较大、加密效率较低的问题,将彩色图像转换为三个层面上的二维灰度图像进行加工处理,加快了加密速度。为了提高算法的鲁棒性,将混沌序列改进为一种均匀分布的序列,得到了更理想的伪随机特性。针对单一混沌加密算法安全性较差的问题,将Logistic映射与Chebyshev映射相结合,获得了复杂性较高的双混沌系统。利用双混沌系统生成的混沌序列有效实现了像素混淆与扩散,对图像加密方法进行了改进。     

基于相位截断菲涅耳变换的彩色图像加密系统

针对相位截断的加密系统无法抵御信息泄露的问题,提出一种基于相位截断菲涅耳变换与随机振幅掩模的加密系统,以抵御信息泄露的问题。将图像分为3个独立的颜色通道,并加入随机幅度掩模通道,对4个通道分别进行菲涅耳衍射截断处理。通过级联处理过程提高了秘钥与密文之间的关联性并消除了信息泄露的风险。最终进行了仿真试验,结果证明,该算法对一般攻击具有较好的鲁棒性,同时解决了信息泄露的问题,优于已有的同类型算法。     

彩色图像加密的新算法研究

最近几年,互联网高速发展,网络技术也突飞猛进,在很多领域,多媒体技术得到了全方位的发展与进步。互联网最为主要的交互对象就是彩色数字图像,其在军事、医疗、政府以及金融等多个领域有着广泛的涉猎,但是在信息传输的过程中,难免会存在一定的安全隐患,需要予以重视。文章对彩色图像加密进行简单介绍,在此基础上,对彩色图像加密的新算法进行研究和分析。     

基于分数傅立叶变换和相位恢复算法的彩色图像加密

提出一种基于分数傅立叶变换和相位恢复算法的彩色图像加密技术。加密时把待加密彩色图像分解为红（R）、绿（G）、蓝（B）三个分量,并构成联合图,然后将联合图迭代编码到两块相位板中,在迭代过程中,同时改变两块相位板。解密时,只需要将编码得到的两块相位板匹配起来放在正确的位置,就可以恢复出高质量的彩色图像。模拟实验表明,该算法收敛速度快,系统安全性能高,并且可以光学实现。     

基于分数傅里叶变换的双彩色图像加密

为了实现单通道双彩色图像的同时加密,首先将两幅待加密的彩色图像转换成索引图像的形式,保留索引图像的颜色映射矩阵,然后仅对数据矩阵采用复数合成、分数傅里叶变换、随机调制实现了双图像的加密。结果表明,只有在使用完全正确密钥的情况下才能恢复出两幅无失真的图像。该算法具有很高的安全性。     

一种基于m序列的图像随机加密与实时传输方案

提出了一种基于m序列的图像随机加密与实时传输方案。在加密时用m序列构造的相位函数取代了双相位输码方法中用作密钥的随机相位掩模，极大地压缩了密钥的数据量，使密钥的传送更加方便快捷。并在前有基础上加以改进，可以轻松地加密彩色图像。在完成加密后，可实时地在网络上传送加密图像，在接收端进行解密。最后进行了计算机模拟实验，实验结果表明该方案是可行的，并且易于实际应用。     

一种Unicode文本伪图像化加密方案

使用Unicode的主要意义在于可以满足跨平台、跨语言的文本处理和转换。为了提高文本信息在传输中的安全,可采用文本的Unicode编码嵌入图像并进行图像加密的方法,由于文本信息与图像信息在计算机中的存储表达均采用二进制,将文本信息嵌入无规则的图像中,再对图像进行读取,在未知文本位置及编码结构的情况下是难以与像素信息加以区分的。实践证明使用Logistic混沌理论进行图像加密可以达到比较理想的效果,应用图像加密手段加密文本信息可以有效提高信息的安全性。     

基于干涉原理和相位恢复算法的图像加密系统

以基于相位恢复算法和光学干涉原理为基本理论依据,提出了一种新的全相位光学图像加密系统。该加密系统利用一块随机相位板作为加密密钥,在其作用下输入图像被数值加密成两块相位板。这两块相位板的衍射图样视觉上无法分辨其内容,但却包含了解密所需要的信息。加密过程中,加密密钥与待加密图像分别作为输入平面和输出平面上的约束条件,在干涉原理的基础上通过迭代运算得到加密结果,即输入面上不同于加密密钥的另一个相位板的相位分布以及傅立叶频域上的相位分布。加密密钥的引入起到了置乱系统输入面相位分布的作用。解密过程中,加密过程中使用的随机相位板和迭代过程中生成的两块相位板缺一不可。计算机仿真实验结果表明,本文提出的加密系统具有算法收敛快、加密结果不存在非线性双随机相位加密和干涉加密方法中发现的信息泄露问题的优点。     

一种高效的彩色图像加密和解密算法

分析了基于Amold变换的加密方案在加密效果及加密效率方面的不足。提出了一种新的彩色图像加密及解密算法。加密过程将像素的物理位置置乱并映射到不同的色彩空间;解密过程提出了一种针对彩色图像的逆变换算法,使解密的时间仅依赖加密的密钥而不依赖变换周期。仿真分析比较了该算法在加密效果及加密效率方面的优势。实验数据表明,该加密算法的加密效果理想,且加密效率较高,是一种简单、可行的彩色图像加密方法。     

基于编码压缩和加密的图像可逆信息隐藏算法

提出一种编码压缩和加密的图像可逆信息隐藏算 法。计算载体像素预测值与其像素值的差值, 对差值进行哈夫曼编码压缩,通过压缩数据和随机数据加密重构图像,得到载体数据。将哈 夫曼编码的码 表和秘密信息隐藏在载体数据中,实现信息隐藏。在载密数据中提取码表数据和秘密信息, 对加密压缩数 据进行解密,结合码表和预测方法恢复原始图像。实验结果表明,本文算法具有较大的隐藏 容量,不仅能 正确提取秘密信息,还能无损恢复原始图像。     

Chaos-based color image block encryption scheme using S-box

A chaos-based color image encryption scheme using bijection is designed. The whole image is diffused by exclusive or (XOR) operation for random rounds, each color component is separated into blocks with the same size. A bijective function f: B → S between block set B and S-box set S, is built. The corresponding 8 × 8 S-box is dynamically generated by the Chen system with variable conditions. The ciphered image can be obtained after substituting each block with the paired S-box. Numerical simulation and security analysis demonstrate that the scheme is practical in image encryption.     

A new color image encryption scheme based on DNA encoding and spatiotemporal chaotic system

In this paper, a new color image encryption scheme based on DNA operations and spatiotemporal chaotic system is presented. Firstly, to hide the distribution information of the plain image, we convert the plain image into three DNA matrices based on the DNA random encoding rules. Then, the DNA matrices are combined into a new matrix and is permutated by a scramble matrix generated by mixed linear-nonlinear coupled map lattices (MLNCML) system. In which, the key streams are associated with the secret keys and plain image, which can ensure our cryptosystem plain-image-dependent and improve the ability to resist known-plaintext or chosen-plaintext attacks. Thereafter, to resist statistical attacks, the scrambled matrix is decomposed into three matrices and diffused by DNA deletion-insertion operations. Finally, the three matrices are decoded based on DNA random decoding rules and recombined to three channels of the cipher image. Simulation results demonstrate that the proposed image cryptosystem has good security and can resist various potential attacks.     

Robust multiple color images encryption using discrete Fourier transforms and chaotic map

Based on discrete Fourier transforms and logistic-exponent-sine map, this paper investigates an encryption algorithm for multiple color images. In the encryption process, each color image represented in trinion matrix is performed by block-wise discrete trinion Fourier transforms. Then the first real matrix is constructed by splicing real and imaginary parts of transformed results. Followed by two-dimensional discrete Fourier transform, the second real matrix is synthesized only using half of the spectrum on the basis of the conjugate symmetry property. In order to further enhance the randomness of interim result, the random multi-resolution singular value decomposition is exploited. Afterwards, a sharing process is utilized to get final cipherimages. Numerical simulations performed on 300 color images have shown that quality of correctly decrypted images is much better, where the PSNR value is up to 305.03 dB. The number of changing pixel rate and unified average changing intensity are respectively greater than 99.99% and 33.33%, indicating good sensitivity. The comparison with other methods under noise and cropping attacks validates the reliability of the proposed algorithm.     

Double color image encryption based on fractional order discrete improved Henon map and Rubik’s cube transform

A double color image encryption method based on DNA (deoxyribonucleic acid) computation and chaos is proposed. Differently from the conventional algorithms, double color images are encrypted at the same time so that we can save information of each other, which makes the encryption more safe and reliable. In addition, a new chaotic fractional order (FO) discrete improved Henon map (FODIHM) is proposed as a pseudo-random number generator. To ensure the plain-image sensitivity of the encryption algorithm, the initial value of FODIHM is calculated from the hash value of the color image (SHA-256) and from the three additional keys entered by the user. Furthermore, a Rubik’s cube transform scrambles the pixels in each color component of the two images. Then, each pixel in each color component of the two images is diffused by means of different DNA coding rules. Finally, the CAT transform, based on FO discrete Logistic map and the classic XOR, is used to further improve the security performance. The key space size of the proposed algorithm is of order $10^{135}$, which is about 30 orders of magnitude higher than those available in the literature. The information entropies are 7.9974 and 7.9973, which are very close to the ideal entropy value of 8. The values of the unified average changing intensity (NPCI) are 99.630 and 99.623, while the number of pixels change rate (UACR) are 33.473 and 33.553, which are also close to the ideal NPCR and UACR value of 99.6094 and 33.4635, respectively. The numerical results and security analysis prove that the algorithm has good resistance to several classic attacks.     

纯相位图象的实值编码

一种用于纯相位图象加密的实值编码方法 ,待编码的纯相位图象与一个随机相位掩膜一起作傅立叶变换 ,取其实部作为编码图象。已编码的图象和随机相位掩膜的傅立叶变换相加作傅立叶反变换 ,记录反变换的光强分布 ,再通过图象灰度变换可以恢复图象。该编译码方法简单 ,编码图象是一个实值图象 ,便于计算机打印或显示输出     

Elliptic curve ElGamal based homomorphic image encryption scheme for sharing secret images

This paper proposes an encryption scheme with a new additive homomorphism based on Elliptic Curve ElGamal (EC-ElGamal) for sharing secret images over unsecured channel. The proposed scheme enables shorter key and better performance than schemes based on RSA or ElGamal. It has a lower computation overhead in image decryption comparing with the method that uses other additively homomorphic property in EC-ElGamal. Elliptic curve parameters are selected to resist the Pohlig-Hellman, Pollard's-rho, and Isomorphism attacks. Experimental results and analysis show that the proposed method has superior performance to RSA and ElGamal.     

色差图像的数字图像拼接算法

针对有明显色彩和亮度差异的图片,在进行传统的图像拼接后,会产生肉眼可见的拼接缝,严重影响拼接效果。因此,提出一种针对存在色差的图像拼接算法。首先,计算相邻图片间的色彩校正参数和每个彩色通道的全局色彩调整参数,选择适合的颜色和亮度,对每一幅图片进行色彩校正。其次,引入SIFT和RANSAC算法,实现了图像的准确配准。最后,采取0．1加权融合算法和平均融合算法结合进行图像融合,得到最终的全景图像。实验结果表明,由于已经进行图像间的校正,减少了待拼接图像的色差,使得图像的融合更加简单。该算法对于存在色差的图片序列可以实现无缝快速的拼接,并且可根据需要调整图像的色彩和亮度。