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Optical Engineering

Experimental demonstration of the random phase encoding technique for image encryption and security verification

Bahram Javidi, Guanshen Zhang, Jian Li

Published Sep 1, 1996• 110 citations
Publisher

Abstract

Optical image encryption and security using random phase encoding techniques have been proposed recently. We present optical experimental results for image encryption and security. The results show that for the image encryption, the image can be well encrypted using random phase masks with a limited number of pixels. We also tested the performance of the optical system for security verification in the presence of different types of input noise and distortions such as scratches, fingerprint marks, and bending of the phase mask. The experimental results indicate that for the severity of the noise and the degree of distortion tested here, the system provides good performance in verifying the phase code.

DOI
10.1117/1.600854

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Optical image encryption and security using random phase encoding techniques have been proposed recently. We present optical experimental results for image encryption and security. The results show that for the image encryption, the image can be well encrypted using random phase masks with a limited number of pixels. We also tested the performance of the optical system for security verification in the presence of different types of input noise and distortions such as scratches, fingerprint marks, and bending of the phase mask. The experimental results indicate that for the severity of the noise and the degree of distortion tested here, the system provides good performance in verifying the phase code.
A fully phase image encryption technique which uses double random phase encoding method is presented. The encryption method can be implemented optically. Robustness of the fully phase encryption and amplitude based encryption in the presence of noise is investigated. Using computer simulations, mean squared error for the decrypted images are obtained. The fully phase based encryption is shown to be robust with respect to the additive noise added to the encrypted image in terms of the mean squared metric. Based on the tests conducted in this paper, the fully phase based encryption method shows better performance than the amplitude based encryption in terms of mean square error metric.
We propose a novel optical information encryption and authentication scheme that uses asymmetric keys generated by the phase-truncation approach and the phase-retrieval algorithm. Multiple images bonded with random phase masks are Fourier transformed, and obtained spectra are amplitude- and phase-truncated. The phase-truncated spectra are encoded into a single random intensity image using the phase-retrieval algorithm. Unlike most of the authentication schemes, in this study, only one encrypted reference image is required for verification of multiple secured images. The conventional double random phase encoding and correlation techniques are employed for authentication verification. Computer simulation results and theoretical explanation prove the effectiveness of the proposed scheme.
In this paper, we propose a new optical security technique using two phase masks based on interferometer. A binary random phase image is used as a reference image and the encrypted image is generated according to the phase difference between the reference image and the original image. If there is no phase difference of a same pixel position in two phase masks, interference intensity of the pixel has minimum value and if phase difference of a same pixel position in two phase masks is , its interference intensity has maximum value. We can decrypt the original image by putting two phase masks on each of the two optical paths of the Mach-Zehnder interferometer. Computer simulation and the optical experiments show a good performance of the proposed optical security system.
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.
Abstract For the purpose of alleviating the vulnerability of double random phase encryption system in the linear canonical transform domain, a novel approach for optical security and cryptographic systems is presented. This proposed system uses a fully phase encoding technique to augment the security of encryption system in the linear canonical transform. The first step in this system involves phase encoding of the initial amplitude image to be ciphered and then modulated by the phase masks. The decryption process of image is the reversal operation of the encryption method. The effectiveness and sensitivity of our proposed cryptosystem for the encryption secret keys are verified. The resistance of our method against occlusion attacks is investigated. Moreover, the results demonstrate that the fully phase-based optical cryptosystem is more secure and robust than the amplitude-based scheme in a linear canonical domain.
We present a compact optical encryption scheme by using a continuous-random-motion blurring model in an optical imaging system. Image encryption is performed by additive motion blur effects with continuous and random shifts of a camera. Real-time random phase modulation can be achieved without the use of random phase mask. Storage of the key is more convenient, which only requires parameters of motion. In addition, modulation characteristics are different from the traditional encryption schemes. On the premise of high security, modulation space is broadened, and flexibility of encryption is further improved. Simulations and experiments verify the validity of the motion blur-based crypto-system and demonstrate its security under several attacks. This novel method will be significant for the practical applications in the field of optical information security.