基于非对称密码系统的彩色图像加密技术

为了实现对彩色图像的加密,提出一种基于傅里叶变换和非对称密钥加密系统的加密方法。把彩色图像分成三基色分量:红,绿,蓝。然后对这3帧灰度图像的傅里叶频谱进行截取,合成一个目标图像,该目标图像包含了原始彩色图像的大部分信息。对此目标图像的幅度和相位分别用非对称密钥加密系统加密,即实现了彩色图像的加密。 给出了理论分析和计算机模拟结果,实验结果证实了该方法的可行性。     

一种单通道彩色图像加密方法

提出了一种彩色图像的单通道加密方法. 在该方法中,首先采用三色光栅编码原理将一幅彩色图像编码为一幅灰度图像,再利用双随机相位加密技术对其加密,从而实现了彩色图像的单通道加密. 该方法既保证了安全性,同时在加密时仅需要一个相干光源,简化了系统,实用性较强. 模拟实验结果证明了其有效性. 关键词： 彩色图像 单通道加密 三色光栅 双随机相位     

基于计算全息和θ调制的彩色图像加密方法

提出了一种基于计算全息和θ调制的彩色图像光学加密新方法.该方法利用彩色三基色原理和计算全息编码技术,首先将彩色图像的红、绿、蓝三基色分量进行随机相位调制和菲涅耳衍射变换,然后经过θ调制后进行图像叠加并编码为计算全息图,即加密过程是将一幅彩色图像加密为一幅实值的二元计算全息图,得到单幅密文.解密为加密的逆过程,首先将加密的计算全息图置于空间滤波和菲涅耳衍射系统中,经过相位密钥解调和基于滤光片的滤波器滤波,最后通过正确距离的菲涅耳衍射完成解密,得到彩色明文图像.计算机模拟结果证明了该方法的有效性和可行性.     

结合计算全息与混沌的彩色图像加密方法

针对现有彩色图像光学加密方法存在解密结果失真的问题,提出一种结合混沌运算与菲涅耳衍射全息的彩色图像单通道加密新方法.首次加密操作利用菲涅耳衍射将彩色图像RGB通道分量转换成一幅实值计算全息图;第二次加密操作是利用改造的Logistic混沌系统对计算全息图像素进行置换与扩散.结果 表明,本文方法除传统混沌系统密钥以外,菲涅耳衍射距离、参考光波长和入射角方向余弦作为关键密钥均可以增大密钥空间(约为10249),而且具有较小的密钥体积;解密图像的保真度高且相邻像素相关性、信息熵、像素数改变率和归一化改变强度等评价指标均接近理想值;密文图像的直方图平坦,灰度分布均匀,完全隐藏了原始彩色图像的灰度和色彩信息.     

基于附加密钥复用的彩色图像加密技术

为了避免使用复数来密文记录和传输彩色图像,提出一种基于附加密钥复用的彩色图像加密方法。先把彩色图像分成三基色分量:红、绿、兰;选取3个独立的附加密钥分别对这3个分量使用改进的光学联合相关变换法加密,得到3个联合功率谱。把这3个联合功率谱进行叠加,得到的复合联合功率谱即加密结果,其包含了原始彩色图像的全部信息。解密时,使用加密时所用的3个附加密钥分别对此复合联合功率谱进行解密,即可正确地重建原始图像的红、绿、蓝分量,进而恢复出原始图像。计算机仿真结果表明,本方法可以将一幅原始彩色图像隐藏于单幅强度图像之中。由于记录强度图像无需参考光波,因此本方法在加密过程中成功地避免了干涉装置,降低了对加密环境的要求。此外,相比于其他彩色图像隐藏方法需要加密至复数密文之中,本方法的密文大小仅为其二分之一,加密效率提高了一倍。     

物理光学 光的干涉与衍射

O436.12006010030正弦光栅条纹的灰度三角细分法=Gray triangle stripmultiplication method to sine grating[刊,中]/于复生(山东建筑工程学院机电工程学院.山东,济南(250014)),沈孝芹∥半导体光电.—2005,26(4).—366-368提出了一种基于灰度三角值的正弦光栅条纹细分法,该方法以CCD拍摄的正弦光栅图像的各点灰度值映射为该点的正弦三角函数值进行处理。给出了原理说明和对图像细分的实例,并对该方法的抗噪性能进行了分析。实验表明即使在图像含有高频噪声污染的情况下,该方法仍具较高的有效性。图3参8(严寒)O436.12006010031倾斜多焦点…     

基于随机分数傅里叶变换的双图像加密算法

利用光学随机分数傅里叶变换设计了一种双图像加密算法,并给出了相应的光学实现.加密算法中,将两幅原始图像分别作为加密系统输入复函数的振幅和位相分布函数,利用随机分数傅里叶变换进行加密,所得复函数的振幅即为加密图像,而位相部分是变换的输出相位,随机位相作为加密算法的密码.在数值模拟中,二值文本图像和灰度图像分别被作为原始图像用于加密结果分析和加密安全测试,结果表明该加密算法具有很好的安全性.     

利用三色光栅实现彩色图像相减

本文提出了一种彩色图像相减的新方法.该方法利用互相错动半个周期的两组三色光栅,在黑白底片上分别对待处理的两幅图像进行一次编码记录,然后在白光处理器上对黑白编码片进行彩色译码,即可实现彩色图像的强度相减,文中讨论了三色光栅实时生成和两组三色光栅条纹自动错动半个周期的方法,并给出了实验结果。     

利用不同空间频率的组合光栅实现任意进制的光逻辑计算和光学加密

利用阿贝成像和θ调制原理实现了任意进制光逻辑计算以及彩色与灰度图像加密.在8f系统中,前后2次输入采用空间频率和取向不同的光栅组合时,滤波面上的图像将呈现高度的几何对称性,即所谓"大圆套小圆"的模型,进行2次空间滤波后,可以调控像屏上的图像输出,实现任意进制的逻辑计算,并可进一步应用于彩色或灰度图像的加密.利用电寻址液晶光阀系统进行实验,结合Mathematica软件的计算机模拟,证明了该方案的可行性.     

基于正弦光栅调制的相位恢复

提出一种基于正弦光栅调制的相位恢复方法.首先,在空间光调制器上加载两个不同方向的正弦光栅对光场复振幅进行调制;然后,推导强度信息和相位偏导数之间的关系式;最后由强度信息计算相位偏导数,进而恢复相位.实验分别测试了该方法对简单图像、复杂图像以及含噪声图像的恢复能力.实验结果表明,该方法可以通过方便地控制图像移动量来有效恢复相位信息,适用于不同尺度的相位物体的计算.     

Improved algorithm for image encryption based on stochastic geometric moiré and its application

A technique based on optical operations on moiré patterns for image encryption and decryption is developed. In this method, an image is encrypted by a stochastic geometric moiré pattern deformed according to the image reflectance map. The decryption is performed using pixel correlation algorithm in the encrypted image and the stochastic geometrical moiré pattern. The proposed technique has a number of advantages over existing encryption techniques based on moiré gratings. No original moiré grating can be reconstructed only from the encrypted image. Stochastic moiré grating can be deformed in any direction what is an important factor of encryption security. Finally, the quality of the decrypted image is much better compared to decryption methods based on the superposition of the regular and deformed moiré gratings. The proposed technique has a great potential, because the process is performed using computational algorithms based on optical operations and optical components are avoided.     

Image encoding based on coherent superposition and basic vector operations

A new method for image encryption based on optical coherent superposition and basic vector operations is proposed in this paper. In this encryption, the original image can be directly separated into two phase masks (PMs). One is a random phase mask (RPM) and the other is a modulation of the RPM by the original image. The mathematical calculation for obtaining the two PMs is quite simple and direct resulting from the simple principle of optical coherent superposition. The arbitrarily selected RPM can be treated as the encrypted result while the PM can be taken as the key for decryption. With this technique, the same encrypted result can be obtained for different images with the same size while the keys for decryption are different. The encryption can be performed digitally and the decryption can be performed optically or digitally. The security of the proposed method is discussed and computer simulation results are presented to verify the validity of proposed method.     

彩色全息图的计算机产生和数字再现

提出了一种基于色彩合成以及菲涅尔衍射原理,用计算机产生全息图并用数字方法再现彩色全息图的方法。该方法的第一步是将物体的彩色RGB图像分离为三基色强度图,再利用博奇编码的方法制成修正离轴参考光分色计算机全息图;第二步是分别对分色全息图在频域进行调制以实现用原参考光真实再现原始物光波。通过滤波消除零级衍射及共轭像的影响,获得了所需要的实像并提高了像质。提供的实验是选用一幅RGB图像作为原始物体,给出了用博奇编码法制成的全息图以及最后经色彩合成获得的再现像。结果表明,该方法能使各分色全息图的再现像准确重合,解决了在色彩合成时容易出现的色串扰问题。     

Multiple color-image fusion and watermarking based on optical interference and wavelet transform

A novel multiple color-image fusion and watermarking using optical interference and wavelet transform is proposed. In this method, each secret color image is encoded into three phase-only masks (POMs). One POM is constructed as user identity key and the other two POMs are generated as user identity key modulated by corresponding secret color image in gyrator transform domain without using any time-consuming iterative computations or post-processing of the POMs to remove inherent silhouette problem. The R, G, and B channels of different user identity keys POM are then individually multiplied to get three multiplex POMs, which are exploited as encrypted images. Similarly the R, G, and B channels of other two POMs are independently multiplied to obtain two sets of three multiplex POMs. The encrypted images are fused with gray-level cover image to produce the final encrypted image as watermarked image. The secret color images are shielded by encrypted images (which have no information about secret images) as well as cover image (which reveals no information about encrypted images). These two remarkable features of the proposed system drastically reduce the probability of the encrypted images to be searched and attacked. Each individual user has an identity key and two phase-only keys as three decryption keys besides transformation angles regarded as additional keys. Theoretical analysis and numerical simulation results validate the feasibility of the proposed method.     

Secret Communication Systems Using Chaotic Wave Equations with Neural Network Boundary Conditions

In a secret communication system using chaotic synchronization, the communication information is embedded in a signal that behaves as chaos and is sent to the receiver to retrieve the information. In a previous study, a chaotic synchronous system was developed by integrating the wave equation with the van der Pol boundary condition, of which the number of the parameters are only three, which is not enough for security. In this study, we replace the nonlinear boundary condition with an artificial neural network, thereby making the transmitted information difficult to leak. The neural network is divided into two parts; the first half is used as the left boundary condition of the wave equation and the second half is used as that on the right boundary, thus replacing the original nonlinear boundary condition. We also show the results for both monochrome and color images and evaluate the security performance. In particular, it is shown that the encrypted images are almost identical regardless of the input images. The learning performance of the neural network is also investigated. The calculated Lyapunov exponent shows that the learned neural network causes some chaotic vibration effect. The information in the original image is completely invisible when viewed through the image obtained after being concealed by the proposed system. Some security tests are also performed. The proposed method is designed in such a way that the transmitted images are encrypted into almost identical images of waves, thereby preventing the retrieval of information from the original image. The numerical results show that the encrypted images are certainly almost identical, which supports the security of the proposed method. Some security tests are also performed. The proposed method is designed in such a way that the transmitted images are encrypted into almost identical images of waves, thereby preventing the retrieval of information from the original image. The numerical results show that the encrypted images are certainly almost identical, which supports the security of the proposed method.     

基于SIFT图像特征区域的全息水印技术

为了增强水印的不可见性和鲁棒性,提出了一种基于图像特征区域的水印算法。首先利用SIFT(Scale Invariant Feature Transform)算法从载体图像蓝色B通道中提取图像特征点来进行优化和筛选,根据优化后的稳定特征点及其特征尺度确定图像的特征区域,再结合全息技术,对原始水印图像进行双随机相位加密,生成加密全息水印;然后对特征区域进行离散余弦变换(DCT);最后在其中频区域嵌入加密全息水印。在提取水印时无须借助原始图像,是盲水印技术。实验结果表明:该算法重建的水印图像与原始水印图像的NC值高达0.95;水印的嵌入对图像质量影响很小,PSNR值高达55.97,能够抵抗常规信号攻击及缩放、剪切、平移等几何攻击。     

Color image encryption based on orthogonal composite grating and double random phase encoding technique

A new method of color image encryption based on orthogonal composite grating and double random phase encoding technique is proposed. The red (R), green (G) and blue (B) components of a color image to be encrypted is modulated into an orthogonal composite grating. The deformed composite grating is subsequently encrypted using double random phase encoding technique. At the decoding end, the deformed composite grating is decrypted through double random phase decoding system. By filtering in frequency domain and phase demodulating, the modulated RGB components can be recovered. Computer simulation experiments have proved the validity of the new method. The proposed method is also applicable to encrypt three color images simultaneously after they have been transformed respectively into indexed formats.     

Optical color image encryption with redefined fractional Hartley transform

We propose a new method for color image encryption by wavelength multiplexing on the basis of two-dimensional (2-D) generalization of 1-D fractional Hartley transform that has been redefined recently in search of its inverse transform. A color image can be considered as three monochromatic images and then divided into three components and each component is encrypted independently with different wavelength corresponding to red, green or blue light. The system parameters of fractional Hartley transform and random phase masks are keys in the color image encryption and decryption. Only when all of these keys are correct, can the image be well decrypted. The optical realization is then proposed and computer simulations are also performed to confirm the possibility of the proposed method.     

Gray images embedded in a color image and encrypted with FRFT and Region Shift Encoding methods

In this paper, we have proposed a new multiple image encryption and watermarking technique. Several gray images can be watermarked in the three channels of an enlarged color image. The neighbor pixel value addition and subtraction algorithm is used to realize blind watermarking, therefore the original host color image does not need in extraction the watermark image. The gray images are encrypted with FRFT and Region Shift Encoding techniques before hiding to enhance the security. The robustness against occlusion attacks and noise attacks are also analyzed. And some computer simulations are presented to verify the possibility.