共查询到18条相似文献,搜索用时 109 毫秒
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基于随机相位实值编码的光学图像加密 总被引:7,自引:7,他引:0
提出了一种用于图像加密的随机相位实值编码方法,待编码的纯相位图像与一个随机相位掩膜一起作傅里叶变换,取其实部作为编码图像.已编码的图像和随机相位掩膜的傅里叶变换相加作傅里叶反变换,反变换的光强可以准确地重建原图像.该编译码方法简单,编码图像是一个实值图像,便于计算机打印或显示输出. 相似文献
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双随机相位图像加密的实值编码研究 总被引:7,自引:5,他引:2
提出了一种基于双随机相位的图像实值编码方法,该方法可应用于光学图像加密.要编码的纯相位图像分别在空间域和频域加入随机相位掩膜,其中在频域将编码范围扩大4倍,经过光学系统的变换,将生成的图像取实部作为编码图像.实值编码的图像利用与编码过程类似的方法进行解码,可以准确地重建原图像.该编译码方法简单,编码图像是一个近似随机噪声的实值图像,便于数字图像的传输与输出. 相似文献
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基于级联分数傅里叶变换系统的数字水印技术 总被引:1,自引:0,他引:1
提出一种基于分数傅里叶变换和随机相位编码的光学加密数字水印技术,可成为一种信息隐藏及保护的有效方案.该数字水印技术对于噪音叠加和常见的图像处理操作具有较强的稳健性.该技术根据光学级联分数傅里叶变换系统,利用两个随机相位分布函数对水印信息编码并经过迭代分数傅里叶变换嵌入到变换域的载体图像中.在水印检测和提取过程中,两个相位分布函数作为密钥.随机相位编码技术的引入,进一步提高了数字水印系统的密钥空间.增强了系统的安全性.该数字水印技术基于光学分数傅里叶变换原理,可以利用光学变换系统方便地实现. 相似文献
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分数傅里叶变换计算全息 总被引:1,自引:0,他引:1
在计算全息和分数傅里叶变换的基础上提出了不对称分数傅里叶变换计算全息和双随机相位不对称分数傅里叶变换计算全息。在这种方法中,首先用一随机相位函数乘以输入图像信息,然后沿x方向实施α级次的一维分数傅里叶变换,再乘以第二个随机相位函数,最后,沿y方向实施β级次的一维分数傅里叶变换。采用迂回位相编码法对变换后的结果编码,绘出计算全息图。为了恢复原始图像,需要知道变换级次和随机相位函数。利用这种方法进行图像加密,使加密图像的密钥由原来两重增加到四重,从而提高了系统的保密性能。 相似文献
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提出一种新的基于信息光学的数字水印方法。该方法将水印信息隐藏于半色调编码的计算全息图之中。通过相位复原技术将需隐藏的水印信息编码为相位函数嵌入在复波前中,其振幅定义为宿主图像,通过计算全息记录复波前并对全息图进行半色调编码完成水印信息的嵌入。水印的提取过程只需对含有水印信息的半色调图像进行光学或数字的傅里叶变换即可完成。并给出了算法有效性的理论分析和仿真实验结果。结果证明这种水印技术对于各种数字图像处理操作具有很高的稳健性,且半色调编码图的二值特性使嵌入水印具有很强的抗打印、抗复印、抗扫描的能力。 相似文献
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为了阐明相位编码光学加密算法的扩散及混淆特性,基于傅里叶变换位移定理,从分组密码设计准则出发,以双随机相位光学加密算法为研究对象,分析了采用单个随机相位模板的2 f系统的扩散和混淆特性。将单随机相位加密过程分解为2个相互关联的过程,结果表明,傅里叶变换在加密算法中引入了混淆操作,而傅里叶变换结合随机相位模板实现了扩散操作。通过数值模拟对上述理论分析进行了验证,引入信息熵来评价加密图像的统计分布特性,进一步分析了菲涅尔域及分数阶傅里叶变换域随机相位加密算法的扩散混淆特性。研究表明,单随机相位加密和双随机相位加密图像的信息熵分布为7.038和7.157,而随机振幅加密图像信息熵为4.521。因而,随机相位加密算法比随机振幅加密算法能实现对信息更好地扩散。 相似文献
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In this paper, we implement a fully phase-encrypted memory system using cascaded extended fractional Fourier transform (FRT). We encrypt and decrypt a two-dimensional image obtained from an amplitude image. The full phase image to be encrypted is fractional Fourier transformed three times and random phase masks are placed in the two intermediate planes. Performing the FRT three times increases the key size, at an added complexity of one more lens. The encrypted image is holographically recorded in a photorefractive crystal and is then decrypted by generating through phase conjugation, the conjugate of the encrypted image. A lithium niobate crystal has been used as a phase contrast filter to reconstruct the decrypted phase image, alleviating the need of alignment in the Fourier plane making the system rugged. 相似文献
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An asymmetric single-channel color image encryption based on Hartley transform and gyrator transform
A novel asymmetric single-channel color image encryption using Hartley transform and gyrator transform is proposed. A color image is segregated into R, G, and B channels and then each channel is independently Hartley transformed. The three transformed channels are multiplied and then phase- and amplitude truncated to obtain first encrypted image and first decryption key. The encoded image is modulated with a conjugate of random phase mask. The modulated image is gyrator transformed and then phase- and amplitude truncated to get second encrypted image and second decryption key. The asymmetric (decryption) keys, random phase mask, and transformation angle of gyrator transform serve as main keys. The optoelectronic encryption and decryption systems are suggested. Numerical simulation results have been demonstrated to verify the performance and security of the proposed security system. 相似文献
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We propose a practical image hiding method using phase wrapping and real-valued decoding key. A zero-padded original image,
multiplied with a random-phase pattern, is Fourier transformed and its real-valued data denotes an encoded image in the embedding
process. The encoded image is divided into two phase-encoded random patterns which are generated based on the phase wrapping
rule. The imaginary part and the real part of these phase-encoded random patterns are used as a hidden image and a decoding
key, respectively. A host image is then made from the linear superposition of the weighted hidden image and a cover image.
The original image is simply obtained by the inverse-Fourier transform of the product of the host image and the decoding key
in the reconstruction process. The embedding process and the reconstruction process are performed digitally and optically,
respectively. Computer simulation and an optical experiment are shown in support of the proposed method. 相似文献
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Image encryption based on extended fractional Fourier transform and digital holography technique 总被引:1,自引:0,他引:1
We present a new optical image encryption algorithm that is based on extended fractional Fourier transform (FRT) and digital holography technique. We can perform the encryption and decryption with more parameters compared with earlier similar methods in FRT domain. In the extended FRT encryption system, the input data to be encrypted is extended fractional Fourier transformed two times and random phase mask is placed at the output plane of the first extended FRT. By use of an interference with a wave from another random phase mask, the encrypted data is stored as a digital hologram. The data retrieval is operated by all-digital means. Computer simulations are presented to verify its validity and efficiency. 相似文献
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In this paper, we have described a simple and secure double random phase encoding and decoding system to encrypt and decrypt a two-dimensional gray scale image. We have used jigsaw transforms of the second random phase mask and the encrypted image. The random phase mask placed in the Fourier plane is broken into independent non-overlapping segments by applying the jigsaw transform. To make the system more secure, a jigsaw transform on the encrypted image is also carried out. The encrypted image is also broken into independent non-overlapping segments. The jigsaw transform indices of random phase code and the encrypted image form the keys for the successful retrieval of the data. Encrypting with this technique makes it almost impossible to retrieve the image without using both the right keys. Results of computer simulation have been presented in support of the proposed idea. Mean square error (MSE) between the decrypted and the original image has also been calculated in support of the technique. 相似文献