Xiulun Yang

Information security system by iterative multiple-phase retrieval and pixel random permutation

A novel information security system based on multiple-phase retrieval by an iterative Fresnel-transform algorithm and pixel random permutation (PRP) technique is proposed. In this method a series of phase masks cascaded in free space are employed and the phase distributions of all the masks are adjusted simultaneously in each iteration. It can achieve faster convergence and better quality of the recovered image compared with double-phase encoding and a similar approach in the spatial-frequency domain with the same number of phase masks and can provide a higher degree of freedom in key space with more geometric parameters as supplementary keys. Furthermore, the security level of this method is greatly improved by the introduction of the PRP technique. The feasibility of this method and its robustness against occlusion and additional noise attacks are verified by computer simulations. The performance of this technique for different numbers of phase masks and quantized phase levels is investigated systematically with the correlation coefficient and mean square error as convergence criterions.

Digital color image watermarking based on phase-shifting interferometry and neighboring pixel value subtraction algorithm in the discrete-cosine-transform domain

A novel single-channel color-image watermarking with digital-optics means based on phase-shifting interferometry (PSI) and a neighboring pixel value subtraction algorithm in the discrete-cosine-transform (DCT) domain is proposed. The converted two-dimensional indexed image matrix from an original color image is encrypted to four interferograms by a PSI and double random-phase encoding technique. Then the interferograms are embedded in one chosen channel of an enlarged color host image in the DCT domain. The hidden color image can be retrieved by DCT, the improved neighboring pixel value subtraction algorithm, an inverse encryption process, and color image format conversion. The feasibility of this method and its robustness against some types of distortion and attacks from the superposed image with different weighting factors are verified and analyzed by computer simulations. This approach can avoid the cross-talk noise due to direct information superposition, enhance the imperceptibility of hidden data, and improve the efficiency of data transmission.

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 users certification image and the quick response code of the user identitys 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 users 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 HMACs irreversible property. Theoretical analysis and numerical simulations both validate the feasibility of our proposed scheme.

Multiple-image authentication with a cascaded multilevel architecture based on amplitude field random sampling and phase information multiplexing

A multiple-image authentication method with a cascaded multilevel architecture in the Fresnel domain is proposed, in which a synthetic encoded complex amplitude is first fabricated, and its real amplitude component is generated by iterative amplitude encoding, random sampling, and space multiplexing for the low-level certification images, while the phase component of the synthetic encoded complex amplitude is constructed by iterative phase information encoding and multiplexing for the high-level certification images. Then the synthetic encoded complex amplitude is iteratively encoded into two phase-type ciphertexts located in two different transform planes. During high-level authentication, when the two phase-type ciphertexts and the high-level decryption key are presented to the system and then the Fresnel transform is carried out, a meaningful image with good quality and a high correlation coefficient with the original certification image can be recovered in the output plane. Similar to the procedure of high-level authentication, in the case of low-level authentication with the aid of a low-level decryption key, no significant or meaningful information is retrieved, but it can result in a remarkable peak output in the nonlinear correlation coefficient of the output image and the corresponding original certification image. Therefore, the method realizes different levels of accessibility to the original certification image for different authority levels with the same cascaded multilevel architecture.

Multiple-Image Encryption Based on Compressive Ghost Imaging and Coordinate Sampling

A multiple-image encryption method that is based on a modified logistic map algorithm, compressive ghost imaging, and coordinate sampling is proposed. In the encryption process, random phase-only masks are first generated with the modified logistic map algorithm; multiple secret images are transformed to be sparsed by the 2-D discrete cosine transformation (DCT) operation and scrambled by different random sequences; the scrambled images are then grouped to one combined image with the help of the coordinate sampling matrices; finally, putting the combined image in the object plane of the compressive ghost imaging system, the ciphertext will be obtained from the buck detector and transferred to the receivers. During the decryption, which is the possession of the correct principle keys and the assistant geometrical parameter key, the original secret images can be successfully decrypted by the logistic map algorithm, measurement matrix generations, compressive sensing reconstruction, DCT distribution extraction, inverse DCT transform, and filtering operation.

Optical information encoding and image watermarking scheme based on phase-shifting interferometry and singular value decomposition

A robust image watermarking scheme based on phase-shifting interferometry (PSI) and singular value decomposition (SVD) is proposed, in which, a grayscale image watermark is encrypted into multiple interferograms using the techniques of double random-phase encoding (DRPE) and PSI. By choosing the appropriate weighting factor, the interferograms are embedded in the singular values of the R, G, and B components of the host image. The scheme achieves a high level of security due to DRPE and at the same time preserves high imperceptibility and robustness due to SVD properties. Simulated results of the proposed scheme are provided to demonstrate the high robustness, not only against the geometric distortion attacks but also against general image processing attacks.

Triple-image encryption based on phase-truncated Fresnel transform and basic vector operation.

A triple-image encryption method is proposed that is based on phase-truncated Fresnel transform (PTFT), basic vector composition, and XOR operation. In the encryption process, two random phase masks, with one each placed at the input plane and the transform plane, are generated by basic vector resolution operations over the first and the second plaintext images, and then a ciphered image in the input plane is fabricated by XOR encoding for the third plaintext image. When the cryptosystem is illuminated by an on-axis plane, assisted by PTFT, the ciphered image is finally encrypted into an amplitude-only noise-like image in the output plane. During decryption, possessing the correct private key, decryption keys, and the assistant geometrical parameter keys, and placing them at the corresponding correct positions, the original three plaintext images can be successfully decrypted by inverse PTFT, basic vector composition, and XOR decoding. Theoretical analysis and numerical simulations both verify the feasibility of the proposed method.

Multilevel image authentication using shared secret threshold and phase retrieval

A new kind of multilevel authentication system based on the (t, n) threshold secret sharing scheme and the iterative phase retrieval algorithm in Fresnel domain is proposed, in which, the first phase distribution iteratively generated is divided into n parts and delivered to n different participants, during high-level authentication, any t (t ≤ n) or more of them can be collected to reconstruct the original meaningful certification image; While in the case of low-level authentication, any t − 1 or fewer will gain no significant information of certification image, however, it can result in a remarkable peak output in the nonlinear correlation coefficient of the recovered image and the standard certification image, which can successfully provide an additional authentication layer for the high-level authentication. Theoretical analysis and numerical simulations both validate the feasibility of our proposed scheme.

An evaluation method for phase shift extraction algorithms in generalized phase-shifting interferometry

A method to evaluate quantitatively the performance of the phase shift extraction algorithms in generalized phase-shifting interferometry (GPSI) is proposed. A parameter named as reconstruction signal-to-noise ratio (R-SNR) is used as the evaluation measure. The R-SNR is defined with the reconstructed object image as the signal and the residual of the DC term and conjugate image as noise. The more accurate the extracted phase shift is, the less residual of the DC term and conjugate image there is, and then the higher R-SNR is obtained. To avoid the overlap of the DC term and conjugate image and the object image, the off-axis digital holography configuration is adopted. The correctness and effectiveness of the proposed method have been verified by both computer simulation and optical experiments. The major advantage of the proposed method is that it utilizes the experimental detectable data and not only the computer simulation results.

Multi-Refraction with Same Polarization State in Two Dimensional Triangular Photonic Crystals

Multi-refraction efiects with one polarization in a two- dimensional triangular photonic crystal (PhC) were systematically studied by theoretical analysis and numerical simulation. The more complicated refraction behaviors can be excited in the higher band regions based on the intricate undulation of one band or the overlap of difierent bands. A novel non-handedness efiect is proposed for the flrst time with group velocity perpendicular to phase velocity. Furthermore, triple refraction phenomena and special collimation efiects of symmetrical positive-negative refraction with the loose incident conditions have been found in difierent band regions of this PhC. These unique features will provide us with more understanding of electromagnetic wave propagation in PhCs and give important guideline for the design of new type optical devices.