Biomolecular optical data storage and data encryption

The use of bacteriorhodopsin (BR) as an active layer in write-once-read-many optical storage is presented. This novel feature of BR materials may be used on a wide variety of substrates, among them transparent substrates but also paper and plastics. The physical basis of the recording process is polarization-sensitive two-photon absorption. As an example for this new BR application, an identification card equipped with an optical recording strip is presented, which has a capacity of about 1 MB of data. The recording density currently used is 125 kB/cm/sup 2/, which is far from the optical limits but allows operation with cheap terminals using plastic optics. In the examples given, data are stored in blocks of 10 kB each. A special optical encryption procedure allows the stored data to be protected from unauthorized reading. The molecular basis of this property is again the polarization-sensitive recording mechanism. The unique combination of optical storage, photochromism, and traceability of the BR material is combined on the single-molecule level. BR introduces a new quality of storage capability for applications with increased security and anticounterfeiting requirements.     

Optical encryption system with a binary key code

A double-random-phase optical encryption system that uses a binary key code is proposed. The key code is generated as a binary computer-generated hologram. The binary key code can be displayed on a binary spatial light modulator (SLM) such as a ferroelectric liquid-crystal display. The use of a binary SLM enables us to renew the key at high speed. A joint transform correlator based on a photorefractive crystal in the Fourier domain is used to perform shift-invariant encryption and decryption. Computer simulations of the effects of using a binary encoded key code instead of a complex amplitude key code are shown. Preliminary optical experimental results are presented to demonstrate the effectiveness of the proposed system.     

Optical encryption by using a synthesized mutual intensity function

We present an optical encryption method for handling time-varying information by means of properly designing a four-dimensional mutual intensity function distribution. We present the theory and validate the basic concept with numerical simulations and experimental results.     

分数傅里叶变换域的彩色图像非对称光学压缩加密

为了提高传统双随机相位编码图像光学加密系统的安全性,并减少其所需要处理的数据量,提出了一种基于压缩感知及量子Logistic混沌映射的彩色图像非对称光学加密方法。针对彩色图像加密过程中所需要处理数据量过大问题,首先利用压缩感知理论减少加密系统所需要处理的数据量,其次,将彩色图像三通道转换为单通道加密来减少数据量。针对传统光学加密系统为线性系统问题,采用基于相位截断的非对称光学加密方法进行加密。针对光学加密系统加密密钥为随机相位板不方便传输问题,利用量子混沌产生系统所需要的随机相位板。结果表明,此算法可以获得较为理想的图像加密和解密效果。     

Optical image encryption system using nonlinear approach based on biometric authentication

A nonlinear image encryption scheme using phase-truncated Fourier transform (PTFT) and natural logarithms is proposed in this paper. With the help of the PTFT, the input image is truncated into phase and amplitude parts at the Fourier plane. The phase-only information is kept as the secret key for the decryption, and the amplitude distribution is modulated by adding an undercover amplitude random mask in the encryption process. Furthermore, the encrypted data is kept hidden inside the face biometric-based phase mask key using the base changing rule of logarithms for secure transmission. This phase mask is generated through principal component analysis. Numerical experiments show the feasibility and the validity of the proposed nonlinear scheme. The performance of the proposed scheme has been studied against the brute force attacks and the amplitude-phase retrieval attack. Simulation results are presented to illustrate the enhanced system performance with desired advantages in comparison to the linear cryptosystem.     

Optical encryption system that uses phase conjugation in a photorefractive crystal

We implement an optical encryption system based on double-random phase encoding of the data at the input and the Fourier planes. In our method we decrypt the image by generating a conjugate of the encrypted image through phase conjugation in a photorefractive crystal. The use of phase conjugation results in near-diffraction-limited imaging. Also, the key that is used during encryption can also be used for decrypting the data, thereby alleviating the need for using a conjugate of the key. The effect of a finite space-bandwidth product of the random phase mask on the encryption system's performance is discussed. A theoretical analysis is given of the sensitivity of the system to misalignment errors of a Fourier plane random phase mask.     

Optical image encryption using password key based on phase retrieval algorithm

A novel optical image encryption system is proposed using password key based on phase retrieval algorithm (PRA). In the encryption process, a shared image is taken as a symmetric key and the plaintext is encoded into the phase-only mask based on the iterative PRA. The linear relationship between the plaintext and ciphertext is broken using the password key, which can resist the known plaintext attack. The symmetric key and the retrieved phase are imported into the input plane and Fourier plane of 4f system during the decryption, respectively, so as to obtain the plaintext on the CCD. Finally, we analyse the key space of the password key, and the results show that the proposed scheme can resist a brute force attack due to the flexibility of the password key.     

Optical colour image encryption using spiral phase transform and chaotic pixel scrambling

In this study, we propose a new optical colour image encryption technique using spiral phase transform and chaotic pixel scrambling. For encryption, three channels of the colour image i.e. red, green and blue are first separated and modulated with three different structured phase masks. Spiral phase transform (SPT) with a particular order of modified spiral phase function (MSPF) is utilized for further processing. Random modulus decomposition is applied to the complex output after SPT to generate the private key for decryption. The pixels of the image are scrambled by using the chaotic Tinkerbell map for enhanced security. The order of MSPF, three structured phase masks, parameters of Tinkerbell mapping, and the private key generated during the encryption process serve as the security keys. The robustness of the proposed method is checked against various potential attacks. A series of numerical simulation results are presented to validate the proposed colour image encryption method.     

Phase-to-amplitude data page conversion for holographic storage and optical encryption

A new phase-to-amplitude data page conversion method is proposed for efficient recovery of the data encoded in phase-modulated data pages used in holographic storage and optical encryption. The method is based on the interference between the data page and its copy shifted by an integral number of pixels. Key properties such as Fourier plane homogeneity, bit error rate, and positioning tolerances are investigated by computer modeling, and a comparison is provided with amplitude-modulated data page holographic storage with and without static phase masks. The feasibility and the basic properties of the proposed method are experimentally demonstrated. The results show that phase-modulated data pages can be used efficiently with reduced system complexity.     

Improvement of digital geographic data quality

The article focuses on the study of characteristics of digital geographical data and the influence of these characteristics on the quality of the basis being ready for the decision-making processes. Characteristics of digital geographical data are mainly described from the point of view of their technical parameters and keeping the technological indicators while obtaining them. Our system brings a user's view into the assessment of characteristics. We define user's requirements on data and suggest the system of their evaluation. The assessment of data characteristics comes out of the standard ISO 19113 and the theory of value analysis. Both systems are joined into a complex system for data evaluation. Technical characteristics of data are evaluated mainly by the level of accomplishment of qualitative indicators, e.g. meeting all requirements of horizontal and vertical mean square error, or by completeness of filling of all expected information. Meeting all users’ requirements is usually expressed by the level of user's satisfaction with the particular product. This level is set based on the survey among users. Simultaneously, the weight of the individual evaluating criteria is set according to specific types of solved tasks. The system of data evaluation is supplemented with a system of calculation of costs that are needed for obtaining the data. It is possible, however, to work either with the complete database, or to count also the influences of particular groups of data (e.g. communications, residential buildings, etc.) on the complete quality of the final product. The system of costs calculation and evaluation of data quality then enables the optimisation of the use of funds or disposable time for obtaining quality data. The use of the complete system is presented in a pilot project in which a model of terrain passability by a military heavy vehicle is solved.     

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.     

Optical image encryption based on compressive sensing and chaos in the fractional Fourier domain

We propose a novel image encryption algorithm based on compressive sensing (CS) and chaos in the fractional Fourier domain. The original image is dimensionality reduction measured using CS. The measured values are then encrypted using chaotic-based double-random-phase encoding technique in the fractional Fourier transform domain. The measurement matrix and the random-phase masks used in the encryption process are formed from pseudo-random sequences generated by the chaotic map. In this proposed algorithm, the final result is compressed and encrypted. The proposed cryptosystem decreases the volume of data to be transmitted and simplifies the keys for distribution simultaneously. Numerical experiments verify the validity and security of the proposed algorithm.     

Optical sectioning with a low-coherence phase-shifting digital holographic microscope

The properties of a low-coherence phase-shifting digital holographic microscope are first studied and analyzed. We then demonstrate en face imaging with transverse resolution of 3 μm and axial resolution of 10 μm through a thickness of 300 μm onion membrane. In addition, with the above said resolutions, optical sectioning of the eye and spine of a live zebra fish has been demonstrated. To the best of our knowledge, this is the first time that a short coherence phase-shifting holographic microscope has been applied to the internal structure visualization of a biological specimen under an in vivo environment.     

Optical triple-in digital logic using nonlinear optical four-wave mixing

A new programmable optical processor is proposed for implementing triple-in combinatorial digital logic that uses four-wave mixing. Binary-coded decimal-to-octal decoding is experimentally demonstrated by use of a photorefractive BaTiO(3) crystal. The result confirms the feasibility of the proposed system.     

Signal processing for multitrack digital data storage

Using a multitrack format in both optical and magnetic data storage applications yields important improvements in system performance, including higher data density and higher data transfer rates. However, the full advantage in data density can be achieved only through the use of joint equalization and joint detection. This paper addresses the complexity of implementing these functions and proposes a transform domain equalization architecture and a reduced-complexity detection method based on a breadth first search of a one-dimensional time-varying representation of a two-dimensional target response. With this method, the complexity of joint equalization and joint detection is not unreasonably greater than that of existing single-track systems and should be feasible for implementation with emerging integrated circuit technologies.