Multidomain asymmetric image encryption using phase-only CGH, QZS method and Umbrella map

In this paper, we have proposed an asymmetric image encryption scheme based on phase only computer generated hologram (CGH), QZ synthesis (QZS) method and Umbrella map. In the proposed algorithm, Umbrella map is used for pixel scrambling in fractional Hartley domain (FrHT)whereas CGH and QZS are employed in Fresnel domain (FrT). The proposed scheme establishes the fact that phase-only computer-generated hologram-based encryption algorithms offer advantages such as the ability to store a large amount of information in a compact space, resistance to counterfeiting, and high security. In the proposed algorithm, Umbrella map provides the additional key to the cryptosystem and QZS provides the plaintext based decryption keys that make it asymmetric. The proposed encryption scheme is validated for grayscale and binary image. The statistical strength of the proposed algorithm is evaluated using information entropy, correlation coefficient, 3-D plots, correlation distribution plots and histogram analysis. The proposed encryption algorithm is robust against all statistical attacks and has also been shown to be robust against contamination attacks. The proposed encryption algorithm is also evaluated against basic cryptographic attacks. The results indicate the effectiveness and robustness of the proposed encryption algorithm to make it a secure cryptosystem.