基于菲涅耳域的双随机相位编码系统的选择明文攻击

用密码分析学的方法对菲涅耳域双随机相位加密系统进行了安全性分析，并提出了一种选择明文攻击的方法，利用多个冲击函数作为选择的明文，成功破解了菲涅耳域的双随机相位加密系统，并给出了密钥的解析式.此方法最大的优点在于解密的无损性，并从理论上加以证明，给出了模拟实验结果. 关键词： 信息光学 双随机相位加密 选择明文攻击 菲涅耳变换     

An improved method to enhance the security of double random-phase encoding in the Fresnel domain

Optical encryption technique based on double random-phase encoding in the Fresnel domain (named as FrDRPE) has been shown to be vulnerable to the chosen-plaintext attack owing to the linear property of the Fresnel transform. To negate such an attack, different phase-masks (i.e. part of the encryption keys of FrDRPE) are used in our system to encrypt different plaintexts while the number of the transmitted keys is not increased. In this case, a plurality of plaintext–ciphertext pairs corresponding to the same encryption key that are needed in the chosen-plaintext attack cannot be acquired by our improved system. Accordingly, this system can successfully resist the chosen-plaintext attack. Some numerical simulations are performed to validate the feasibility of our proposed scheme.     

Chosen-plaintext attack on lensless double-random phase encoding in the Fresnel domain

We demonstrate a method of chosen-plaintext attack on lensless double-random phase encoding (L-DRPE) in the Fresnel domain. With this attack an opponent can access two encryption keys with help of the impulse functions as chosen plaintexts. This shows that a lensless optical encryption scheme based on DRPE is vulnerable to chosen-plaintext attack. Cryptoanalysis also indicates that the security worry originates from the linearity of the encryption and decryption mechanism of the L-DRPE scheme. One of the interesting features of the proposed attack is that the decryption process is lossless. Numerical simulations show good agreement with theoretical analysis.     

Optical multiple-image encryption based on phase encoding algorithm in the Fresnel transform domain

A novel method of the optical multiple-image encryption based on the modified Gerchberg–Saxton algorithm (MGSA) is presented. This proposed method with an architecture of two adjacent phase only functions (POFs) in the Fresnel transform (FrT) domain that can extremely increase capacity of system for completely avoiding the crosstalk between the decrypted images. Each encrypted target image is separately encoded into a POF by using the MGSA which is with constraining the encrypted target image. Each created POF is then added to a prescribed fixed POF composed of a proposed MGSA-based phase encoding algorithm. Not only the wavelength and multiple-position parameters in the FrT domain as keys to increase system security, the created POFs are also served mutually as the encryption keys to decrypt target image based on cascading two POFs scheme. Compared with prior methods [23], [24], the main advantages of this proposed encryption system is that it does not need any transformative lenses and that makes it very efficient and easy to implement optically. Simulation results show that this proposed encryption system can successfully achieve the multiple-image encryption with multiple-position keys, which is more advantageous in security than previous work [24] for its decryption process with only two POFs keys to accomplish this task.     

An image reconstruction method based on the double-random phase encoding system in the Fresnel domain

A method used to reconstruct the image from the frequency spectrum intensity of an encrypted image is proposed in this paper. The encrypted image is obtained by utilizing the double-random phase encoding technology in the Fresnel domain on a symmetrical original image. The frequency spectrum intensity of an encrypted image is received by a CCD, and transformed to a computer. With the help of an algorithm, involving autocorrelation and complex-convolution in the discrete Fresnel transform, a reconstructed image that is the same as the original image could be obtained. Numerical simulation shows that our method is only effective for a symmetrical original image. Discussion on the influence of the deviation of pixel value in the position of symmetry has also been provided in this paper.     

Multiple-image hiding in the Fresnel domain

To avoid additive cross-talk among multiple images, they are separated from each other and even from the host image in the hiding and the extraction process by locating them independently in the Fresnel domain with computer-generated double phase-only masks. Gray images and white-ground and black-ground binary images can be hidden in the system at the same time. The hiding capacity of the system as to these three types of multiple image has also been investigated using a cascaded iterative algorithm. The security and the multiplexing parameters of the system are analyzed as well.     

Double random-phase encryption based on discrete quaternion fourier-transforms

In this paper, a new method for color-image encryption using Discrete Quaternion Fourier-Transforms (DQFT) combined with double random-phase encryption is reported, by which color images can be processed as single channel architecture, instead of as separated color components in three channels, so that the complexity of the encryption system can be effectively reduced without any reduction of its security. The principle of both encryption and decryption is detailed and the noise robustness of the system has been examined experimentally.     

A blind image detection method for information hiding with double random-phase encoding

In this paper, a blind image detection method based on a statistical hypothesis test for information hiding with double random-phase encoding (DRPE) is proposed. This method aims to establish a quantitative criterion which is used to judge whether there is secret information embedded in the detected image. The main process can be described as follows: at the beginning, we decompose the detected gray-scale image into 8 bit planes considering it has 256 gray levels, and suppose that a secret image has been hidden in the detected image after it was encrypted by DRPE, thus the lower bit planes of the detected image exhibit strong randomness. Then, we divide the bit plane to be tested into many windows, and establish a statistical variable to measure the relativity between pixels in every window. Finally, judge whether the secret image exists in the detected image by operating the t test on all statistical variables. Numerical simulation shows that the accuracy is quite satisfactory, when we need to distinguish the images carrying secret information from a large amount of images.     

Securing color image by using phase-only encoding in Fresnel domains

We propose a novel color image hiding scheme with three channels of cascaded Fresnel domain phase-only filtering. The original color image is encoded into three phase masks by using the Gerchberg–Saxton iterative phase retrieval algorithm with another predefined phase key. The individual phase masks are placed in the inputs of the Fresnel domains of the red–green–blue channels and the phase key in the public channel, during the optical retrieval. The physical parameters in the optical system will be regarded as the additional keys for security enhancement. Numerical simulation is performed to test the validity of our scheme.     

基于分频域和菲涅耳域的光学图像加密方法

结合分数傅里叶变换及菲涅耳变换,在光学图像加密系统中分别具有多密钥性和无透镜性的优点,提出了基于分频域和菲涅耳域的光学图像加密方法。基于分数傅里叶变换的光学加密系统,引入菲涅耳变换及全息技术,使原有的加密系统在不增加光学元件的基础上提高了系统的安全性。理论分析和计算机仿真模拟证明了这种方法的可行性。     

多波长同时照明的菲涅耳域非相干叠层衍射成像

传统的叠层衍射成像往往采用单波长照明,即使使用多波长来提升恢复质量也是采用依次照明的方式,同时对相干性要求很高.非相干光照明一直被认为不利于衍射成像.本文提出了一种多波长同时照明的非相干叠层衍射成像方案及相应的多路复用叠层衍射成像算法,并通过仿真和实验验证了该方案的可行性.相比于传统的相干叠层衍射成像方案,该方案不仅能够很好地恢复物像,同时也能够恢复不同波长下分别对应的物体的光谱响应、复振幅探针和光谱比例,从而获得更多的物体信息,具有多通道和多光谱的优势.同时,通过彩色图像编码的方式,能够实现物体的真彩色复原和图像质量的增强.此外,还证明了该算法具有很强的鲁棒性,研究了最多可分辨波长的数量.该研究结果为叠层衍射成像技术的信息多路复用及多光谱成像在更多领域的应用展现了可能性.     

Key rotation multiplexing for multiple-image optical encryption in the Fresnel domain

We introduce a key rotation multiplexing method into the double random phase encoding system for multiple-image optical encryption in the Fresnel domain. Each plaintext is encoded into a stationary-white-noise ciphertext by the same only phase mask located at the input plane, and another only phase mask with a certain rotation angle located at the transform plane. All ciphertexts encoded from different plaintexts are added together to produce a final ciphertext, which serves as a single data source for different plaintexts decryption. Thus, the mask located at transform plane can be utilized to decrypt different plaintexts with a certain rotation angle. Also, we perform computer simulations to investigate how the quantization level of decrypted key and CCD, respectively, affect the decrypted quality and the number of images that can be multiplexed.     

Encrypted optical memory system using three-dimensional keys in the Fresnel domain

An encrypted optical memory system using double random phase codes in the Fresnel domain is proposed. In this system, two random phase codes and their positions form three-dimensional keys for encryption of images and are used as keys to recover the original data. The third dimension is the positions of the codes, which can have as many as three degrees of freedom. Original images encrypted by use of the two phase codes located in the Fresnel domain are stored holographically in a photorefractive material. We demonstrate in preliminary experiments encryption and decryption of optical memory in a LiNbO(3) :Fe photorefractive crystal by use of angular multiplexing.     

Digital audio information hiding based on Arnold transformation and double random-phase encoding technique

In this paper, Arnold transformation and double random-phase encoding technique widely used in digital image information hiding are introduced to digital audio information hiding. The digital audio is transformed into a 2-D image called sound map and then the sound map will be divided into many windows and each window will be encrypted based on the Arnold transformation. Finally sound map will be re-encrypted based on double random-phase encoding technique. This method offers many advantages for digital audio information hiding: improve security and high attack immunity.     

Double image encryption based on linear blend operation and random phase encoding in fractional Fourier domain

A novel method for double image encryption is proposed by using linear blend operation and double-random phase encoding (DRPE) in the fractional Fourier domain. In the linear blend operation, a random orthogonal matrix is defined to linearly recombined pixel values of two original images. The resultant blended images are employed to constitute a complex-valued image, which is encrypted into an encrypted image with stationary white distribution by the DRPE in the fractional Fourier domain. The primitive images can be exactly recovered by applying correct keys with fractional orders, random phase masks and random angle function that is used in linear blend operation. Numerical simulations demonstrate that the proposed scheme has considerably high security level and certain robustness against data loss and noise disturbance.     

菲涅尔双棱镜干涉实验中双棱镜两种放置方法的讨论

在菲涅尔双棱镜干涉实验中,双棱镜有两种不同的放置方法,分析了这两种放置方法中两虚光源的距离、干涉区域范围、干涉条纹间距、干涉条纹数目应相同,因而得到双棱镜的两种放置方法是等价的结论。     

Determination of optimal parameters for detecting the existence of secret information hidden by the double random-phase encoding technique

A new method based on statistical hypothesis detection for information hidden using the double random-phase encoding technique is introduced. According to this method, a series of windows are opened on the lowest bit-plane of image, and an exclusive OR (XOR) operation is performed between different pixels in every window. The results of XOR operation are then analyzed. Using this method, we can judge whether an image contains secret information encrypted by the double random-phase encoding technique. The result of the judgment may be influenced by two parameters, namely the size of the window and the threshold value. A further study is also made to determine the optimal parameters.     

An optical image cryptosystem based on Hartley transform in the Fresnel transform domain

A novel method for image encryption and decryption based on Hartley transform in the Fresnel transform domain is presented. Different from the conventional method which requires lens to perform the Fourier transform for achieving Hartley transform, the proposed new optical architecture of Hartley transform is based on the Fresnel diffraction which requires no Fourier transform lenses. The position coordinate as well as the wavelength in the Fresnel transform is used as encoding keys that can ensure the sufficient information security. The main advantages of this proposed image security system are that it uses fewer optical devices and the decryption scheme is straightforward and more secure than the previous works.