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This paper proposes a Hash based authentication scheme that employs equal modulus decomposition (EMD) and fractional joint transform correlator. An 8-bit grey scale image is separated into its constituent bit plane matrices. Each bit plane matrix is subjected to EMD encryption procedure employing numerically generated random phase mask (RPM) and amplitude mask (AM). The EMD encryption results into two complex functions, which are used for the generation of phase mask and amplitude mask for the next bit plane matrix. A two round EMD procedure is carried out to obtain an 8-bit intensity matrix which is Fourier transformed and its central frequency components are extracted to obtain a 256-bit Hash value. Numerical simulations have been carried out to validate the effectiveness and performance of the proposed scheme. [ABSTRACT FROM AUTHOR]

We propose a method of topological charge number multiplexing based on the JTC encryption system to achieve multiple-image encryption. Using this method, multi-image can be encrypted into single ciphertext, and the original images can be recovered according to the authority level. The number of encrypted images is increased, moreover, the quality of decrypted images is improved. Results of computer simulation and initial experiment identify the validity of our proposed method. [ABSTRACT FROM AUTHOR]

In optical encryption systems, speckle noise is one major challenge in obtaining high quality decrypted images. This problem can be addressed by employing a QR code based noise-free scheme. Previous works have been conducted for optically encrypting a few characters or a short expression employing QR codes. This paper proposes a practical scheme for optically encrypting and decrypting a gray-scale image based on QR codes for the first time. The proposed scheme is compatible with common QR code generators and readers. Numerical simulation results reveal the proposed method can encrypt and decrypt an input image correctly. [ABSTRACT FROM AUTHOR]

We demonstrate an optical image encryption scheme using 3-D chaotic map based joint image scrambling and random encoding in gyrator domains. A novel image confusion approach that can well address the drawbacks of typical image permutation ciphers is developed to firstly shuffle the plaintext. Then the scrambled image is random phase encoded in the spatial domain and gyrator transform domain. A three-dimensional chaotic map is introduced to generate key stream elements. Simulations demonstrate that the cryptosystem has satisfactory cryptographic features and owns high robustness against noise perturbation as well as occlusion attack. [ABSTRACT FROM AUTHOR]

Abstract: In this paper, we show that amplitude- and phase-truncation-based optical asymmetric cryptosystem is vulnerable to known-plaintext attack. The decryption keys are generated with the help of modified Gerchberg–Saxton phase retrieval algorithm from known-plaintext and ciphertext. With the help of the generated keys, the encrypted image, which is encrypted using encryption keys placed in either of the domains (Fourier, Fresnel, or fractional Fourier domain) is decrypted successfully. The vulnerability is proved through the results of computer simulation. [Copyright &y& Elsevier]

Abstract: A novel double image encryption method is proposed by utilizing double pixel scrambling technique and random fractional Fourier domain encoding. One of the two original images is encoded into the phase of a complex signal after being scrambled by one matrix, and the other original image encoded into its amplitude after being scrambled by another matrix. The complex signal is then encrypted into stationary white noise by utilizing double random phase encoding in fractional Fourier domain. By applying the correct keys with fractional orders, the random phase masks and the pixel scrambling operation, the two original images can be retrieved without cross-talk. Numerical simulations have been done to prove the validity and the security of the proposed encryption method. [Copyright &y& Elsevier]

Abstract: A new method for image encryption based on optical coherent superposition and basic vector operations is proposed in this paper. In this encryption, the original image can be directly separated into two phase masks (PMs). One is a random phase mask (RPM) and the other is a modulation of the RPM by the original image. The mathematical calculation for obtaining the two PMs is quite simple and direct resulting from the simple principle of optical coherent superposition. The arbitrarily selected RPM can be treated as the encrypted result while the PM can be taken as the key for decryption. With this technique, the same encrypted result can be obtained for different images with the same size while the keys for decryption are different. The encryption can be performed digitally and the decryption can be performed optically or digitally. The security of the proposed method is discussed and computer simulation results are presented to verify the validity of proposed method. [ABSTRACT FROM AUTHOR]