Abstract
We propose an optical asymmetric single-channel color image cryptosystem based on two-step phase-shifting and random modulus decomposition (RMD) method. In the proposed cryptosystem, a color image is represented by the indexed format including a data matrix and a colormap. The data matrix is regarded as the input of double random phase encoding (DRPE)-based structure while the colormap in which the number of the colors is used as a private key. A designed operator in which phase modulators (PMs) utilized as private keys are generated is introduced to the DRPE-based structure to remove its linearity. As the output of the DRPE-based structure, the complex-valued image is retrieved from interferograms recorded using two-step phase-shifting technique. In addition, to further improve the security of the cryptosystem, the RMD used as a post-processing operation is performed digitally on the retrieved complexed-valued image and then an additional private key is generated. In the decryption process, three private keys generated in the encryption process are utilized to retrieve the original color image using a modified 4-f cryptosystem. In our proposed algorithm, decryption keys are different from encryption keys and the decryption process is also different from the encryption process. Compared to the DRPE-based cryptosystem, the proposed cryptosystem is immune to various attacks. Numerical simulation is carried out to demonstrate the feasibility and effectiveness of the proposed cryptosystem.
Published Version
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