Object authentication in computational ghost imaging with the realizations less than 5% of Nyquist limit

Optical authentication method based on correspondence ghost imaging

Ghost imaging technology has a great application potential in optical security because of its non-local characteristics. In this paper, on the basis of computational ghost imaging, an optical authentication scheme is proposed that utilizes the correspondence imaging technique for the preliminary reconstruction of the object image, and then authenticates the image by a nonlinear correlation algorithm. Different from the previous optical authentication schemes that usually adopted random selection of measurements, this authentication method consciously selects the bucket detector measurement values with large fluctuation and can achieve authentication using ultra-low data volumes less than 1% of the Nyquist limit. In brief, this scheme is easy to implement and has a simpler algorithm and higher stability, which is a tremendous advantage in practical optical authentication systems. The simulation and physical experimental results demonstrate the feasibility of the scheme.

Single-pixel neural network object classification of sub-Nyquist ghost imaging

A single-pixel neural network object classification scenario in the sub-Nyquist ghost imaging system is proposed. Based on the neural network, objects are classified directly by bucket measurements without reconstructing images. Classification accuracy can still be maintained at 94.23% even with only 16 measurements (less than the Nyquist limit of 1.56%). A parallel computing scheme is applied in data processing to reduce the object acquisition time significantly. Random patterns are used as illumination patterns to illuminate objects. The proposed method performs much better than existing methods for both binary and grayscale images in the sub-Nyquist condition, which is also robust to environment noise turbulence. Benefiting from advantages of ghost imaging, it may find applications for target recognition in the fields of remote sensing, military defense, and so on.

Optical information authentication using phase-only patterns with single-pixel optical detection

In this paper, we propose and experimentally demonstrate phase-only authentication based on single-pixel optical imaging through scattering media. The propagating wave is sequentially modulated by using a series of random amplitude-only patterns embedded in a spatial light modulator (SLM), and then a series of one-dimensional (1D) intensity values is recorded by the single-pixel (bucket) detector. Subsequently, an intensity pattern just before the SLM is retrieved by using a correlation algorithm and then further propagates back to the object plane in which the object phase pattern is recovered to serve as reference. Then some single-pixel intensity values are randomly selected from the recorded data, and 1-bit compression is applied to the randomly selected data in order to generate 1D binary signals as ciphertext. A series of random amplitude-only patterns corresponding to the randomly selected single-pixel intensity values serve as principal keys. In a scattering environment, the proposed method is able to carry out phase-only authentication without visually rendering the plaintext, which has not been previously studied. It is found that phase-only authentication is sensitive to security keys, and the proposed method possesses high security. In addition, the proposed method is highly robust to noise contamination and data-loss contamination. Optical experimental results demonstrate the feasibility and effectiveness of the proposed method.

Forgery attack on optical encryption based on computational ghost imaging

Attack techniques on a cryptosystem include not only cryptanalysis, but also forgery and modification of messages, deception and confusion on both sender and receiver sides, and so on. In this Letter, we show that an optical encryption system based on computational ghost imaging (CGI) has security vulnerability owing to its high tolerance for error deviation of ciphertext. It leaves a chance for a forgery attack in which attackers can forge a set of fake keys according to the intercepted ciphertext. If the forged key can be transmitted to the receiver by some disguised means, he/she may be cheated or confused by the retrieved fake images. The discovery of this vulnerability may also help upgrade the CGI-based encryption system.

DeepGhost: real-time computational ghost imaging via deep learning

The potential of random pattern based computational ghost imaging (CGI) for real-time applications has been offset by its long image reconstruction time and inefficient reconstruction of complex diverse scenes. To overcome these problems, we propose a fast image reconstruction framework for CGI, called "DeepGhost", using deep convolutional autoencoder network to achieve real-time imaging at very low sampling rates (10-20%). By transferring prior-knowledge from STL-10 dataset to physical-data driven network, the proposed framework can reconstruct complex unseen targets with high accuracy. The experimental results show that the proposed method outperforms existing deep learning and state-of-the-art compressed sensing methods used for ghost imaging under similar conditions. The proposed method employs deep architecture with fast computation, and tackles the shortcomings of existing schemes i.e., inappropriate architecture, training on limited data under controlled settings, and employing shallow network for fast computation.

Experimental demonstration of ghost-imaging-based authentication in scattering media

Optical imaging in scattering media and its applications are challenging and meaningful. In this paper, we propose and experimentally verify a new optical authentication method using structured-detection-based ghost imaging (GI) in scattering media. Object wave is disturbed by multiple diffusers, and then sequentially modulated by a series of random amplitude-only patterns embedded in a spatial light modulator (SLM). The modulated wave passes through another scattering medium, and its intensity is measured by using a single-pixel bucket detector without spatial resolution. During the decryption and authentication, a reference pattern is first retrieved by using all recorded single-pixel intensity signals. Subsequently, a small number of the recorded single-pixel intensity signals are further randomly selected, and a 1-bit compression operation is applied to these selected intensity signals to generate binary signals as ciphertext. The random amplitude-only patterns corresponding to the selected single-pixel intensity signals serve as principal security keys, and wavelength, axial distance and pixel size can serve as supplementary keys. Two strategies are further developed for the decryption and authentication. It is experimentally verified that the proposed method possesses high robustness and high discrimination capability. The proposed method established by using scattering media can significantly enrich optical security, and provides a promising approach for optical authentication.

Optical image hiding under framework of computational ghost imaging based on an expansion strategy

A novel optical image hiding scheme based on an expansion strategy is presented under the framework of computational ghost imaging. The image to be hidden is concealed into an expanded interim with the same size as the host image. This is implemented by rearranging the measured intensities of the original object after the process of ghost imaging. An initial Hadamard matrix is used to generate additional matrices by shifting it circularly along the column direction, so that enough 2D patterns are engendered to retrieve phase-only profiles for imaging. Next, the frequency coefficients of the host image are modified with that of the expanded interim by controlling a small weighting factor. After an inverse transform, the host image carrying the hidden information can be obtained with high imperceptibility. Security is assured by considering optical parameters, such as wavelength and axial distance, as secret keys due to their high sensitivity to tiny change. Importantly, differing from other computational ghost imaging based schemes, many phase-only profiles are used to collect the measured intensities to enhance the resistance against noise and occlusion attacks. The simulated experiments illustrate the feasibility and effectiveness of the proposed scheme.

X-ray computational ghost imaging with single-pixel detector

We demonstrate computational ghost imaging at X-ray wavelengths with only one single-pixel detector. We show that, by using a known designed mask as a diffuser that induces intensity fluctuations in the probe beam, it is possible to compute the propagation of the electromagnetic field in the absence of the investigated object. We correlate these calculations with the measured data when the object is present in order to reconstruct the images of 50 μm and 80 μm slits. Our results open the possibilities for X-ray high-resolution imaging with partially coherent X-ray sources and can lead to a powerful tool for X-ray three-dimensional imaging.

Computer-generated hologram marked by correlated photon imaging

The computer-generated hologram (CGH) has been studied for many applications. In this paper, CGH is watermarked by correlated photon imaging. An input image is encoded into two cascaded phase-only masks by using the CGH principle. Subsequently, two different marks are independently encoded into one-dimensional (1D) intensity points by using correlated photon imaging (or ghost imaging), and the recorded 1D intensity points are embedded into the extracted phase masks for optical watermarking. During the decoding, the input is recovered by using two watermarked phase masks. To verify copyright of the recovered input image, information embedded in two phase-only masks is retrieved and used to decode the hidden marks. The decoded marks do not visually render clear information due to only a few measurements and, instead, are authenticated. It is illustrated that the quality of the recovered input image is high, and a different imaging approach can be applied in the CGH system for optical watermarking. The proposed approach provides a promising strategy for optical information security.

Computer-generated hologram using binary phase with an aperture

Computer-generated holograms (CGHs) have attracted more and more attention in some application fields, such as 3D displays, optical security, and beam shaping. In this paper, a strategy is presented for optical information verification based on CGH using binary phase (1 bit) with an aperture. The input is encoded into the cascaded phase-only masks based on CGH via iterative phase retrieval, and one extracted phase mask is binarized in which one part is selected according to an aperture and further embedded into a random binary-phase host mask. It is numerically illustrated that the reconstructed image can be effectively verified when system parameters, such as aperture and phase-only masks, are correctly applied. It is demonstrated that the proposed method can provide a promising strategy for CGH-based optical verification.

Ghost identification based on single-pixel imaging in big data environment

In recent years, single-pixel imaging has become one of the most interesting and promising imaging technologies for various applications. In this paper, a big data environment for the first time to my knowledge is designed and introduced into single-pixel ghost imaging for securing information. Many series of one-dimensional ciphertexts are recorded by a single-pixel bucket detector to form a big data environment. Several hidden inputs are further encoded based on ghost imaging by using hierarchical structure, and their corresponding ciphertexts are synthesized into the big data environment for verifying the hidden ghosts and identifying the targeted ghosts. This new finding could open up a different research perspective for exploring more applications based on single-pixel imaging.

Studying fermionic ghost imaging with independent photons

Ghost imaging with thermal fermions is calculated via two-particle interference based on the superposition principle for different alternatives in Feynman's path integral theory. It is found that ghost imaging with fully polarized thermal fermions can be simulated by ghost imaging with fully polarized thermal bosons and classical particles. Photons in pseudothermal light are employed to experimentally study fermionic ghost imaging. Ghost imaging with thermal bosons and fermions is discussed based on the point-to-point (spot) correlation between the object and image planes. The employed method offers an efficient guidance for future ghost imaging with real thermal fermions, which may also be generalized to study other second-order interference phenomena with fermions.

Object authentication based on compressive ghost imaging

Ghost imaging is a transverse imaging technique that allows an object to be reconstructed using the correlation between a pair of light fields. As known, in ghost imaging configurations, a large number of realizations are usually required for reconstruction of the objects. To reduce the number of realizations, Chen et al. [Opt. Lett.38, 546-548 (2013)OPLEDP0146-959210.1364/OL.38.000546] demonstrated an object authentication method with computational ghost imaging using realizations of less than 5% of the Nyquist limit. In this paper, we have further improved this method using a "compressive sensing algorithm" instead of a "classical correlation algorithm in computational ghost imaging." As a result, the realizations for object authentication were further reduced from 5% of the Nyquist limit to 3% of the Nyquist limit.

Digital holography-secured scheme using only binary phase or amplitude as ciphertext

A digital holography-secured scheme is presented by using binary phase or amplitude. The input image is encrypted based on double random phase encoding, and a complex-valued wavefront in the charge-coupled device plane is extracted by using digital holography. Subsequently, only the phase component of the extracted complex-valued wavefront is maintained, and is further binarized. Different from conventional methods, an interesting finding in this paper is that in addition to binary phase, binary amplitude originating from the binarized phase pattern can also be applied as ciphertext. During optical decoding, the decrypted image cannot visually render clear information about the input, and the authentication is further conducted. The binary phase or amplitude pattern can be flexibly applied as ciphertext, and the fully optical approach can be implemented for the decoding. The ciphertext is effectively compressed, which can facilitate the storage and transmission in practical applications.

Efficient asymmetric image authentication schemes based on photon counting-double random phase encoding and RSA algorithms

Recently, double random phase encoding (DRPE) has been integrated with the photon counting (PC) imaging technique for the purpose of secure image authentication. In this scheme, the same key should be securely distributed and shared between the sender and receiver, but this is one of the most vexing problems of symmetric cryptosystems. In this study, we propose an efficient asymmetric image authentication scheme by combining the PC-DRPE and RSA algorithms, which solves key management and distribution problems. The retrieved image from the proposed authentication method contains photon-limited encrypted data obtained by means of PC-DRPE. Therefore, the original image can be protected while the retrieved image can be efficiently verified using a statistical nonlinear correlation approach. Experimental results demonstrate the feasibility of our proposed asymmetric image authentication method.

Spectral Camera based on Ghost Imaging via Sparsity Constraints

The image information acquisition ability of a conventional camera is usually much lower than the Shannon Limit since it does not make use of the correlation between pixels of image data. Applying a random phase modulator to code the spectral images and combining with compressive sensing (CS) theory, a spectral camera based on true thermal light ghost imaging via sparsity constraints (GISC spectral camera) is proposed and demonstrated experimentally. GISC spectral camera can acquire the information at a rate significantly below the Nyquist rate, and the resolution of the cells in the three-dimensional (3D) spectral images data-cube can be achieved with a two-dimensional (2D) detector in a single exposure. For the first time, GISC spectral camera opens the way of approaching the Shannon Limit determined by Information Theory in optical imaging instruments.

Standoff two-color quantum ghost imaging through turbulence

Recently, a two-color quantum ghost imaging configuration was proposed by Karmakar et al. [Phys. Rev. A81, 033845 (2010)]. By illuminating an object located far away from the source and detector, with a signal beam of long wavelength to avoid absorption of short wavelengths in the atmosphere while a reference beam of short wavelength is detected locally, this imaging configuration can be appropriate for standoff sensing. In practice, the signal beam must propagate through atmosphere in the presence of serious turbulence. We analyzed theoretically the performance of this ghost imaging configuration through turbulence. Based on the Gaussian state source model and extended Huygens-Fresnel integral, a formula is derived to depict the ghost image formed through turbulence of a standoff reflective object. Numerical calculations are also given according to the formula. The results show that the image quality will be degraded by the turbulence, but the resolution can be improved by means of optimizing the wavelengths of the reference and signal beams even when the turbulence is very serious.

Optical identity authentication scheme based on elliptic curve digital signature algorithm and phase retrieval algorithm

An optical identity authentication scheme based on the elliptic curve digital signature algorithm (ECDSA) and phase retrieval algorithm (PRA) is proposed. In this scheme, a user's certification image and the quick response code of the user identity's keyed-hash message authentication code (HMAC) with added noise, serving as the amplitude and phase restriction, respectively, are digitally encoded into two phase keys using a PRA in the Fresnel domain. During the authentication process, when the two phase keys are presented to the system and illuminated by a plane wave of correct wavelength, an output image is generated in the output plane. By identifying whether there is a match between the amplitude of the output image and all the certification images pre-stored in the database, the system can thus accomplish a first-level verification. After the confirmation of first-level verification, the ECDSA signature is decoded from the phase part of the output image and verified to allege whether the user's identity is legal or not. Moreover, the introduction of HMAC makes it almost impossible to forge the signature and hence the phase keys thanks to the HMAC's irreversible property. Theoretical analysis and numerical simulations both validate the feasibility of our proposed scheme.