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Asymmetric multiple image encryption using a wavelet transform and gyrator transform

A new asymmetric multiple information security system based on a wavelet transform and gyrator transform is proposed. In the proposed method, a set of four color images are allocated to each user. Each color image is a single-level 2-D discrete wavelet transformed to decompose into LL, HL, LH, and HH sub-bands. The LL sub-bands of four images are fused to obtain a single fused image as an input image, which is segregated into R, G, and B channels. Each channel is compressed by compressive sensing with measurement matrices and modulated by a measurement-matrices-based random phase mask. In similar fashion, n sets of modulated R, G, and B channels are individually multiplexed and then gyrator transformed. The phase of each encrypted channel is embedded into the corresponding channel of the host image to obtain a watermarked channel and its amplitude is used as a common decryption key. Each set has individual decryption keys and chaotic parameters as extremely sensitive decryption keys to ensure the nonlinearity of the system. Thus, it resists potential attacks. The proposed scheme significantly reduces the data volume to be processed, transmitted, and stored, and simplifies the keys to be distributed simultaneously. The retrieved images are devoid of cross-talk noise effects. A simple optoelectronic system can be employed to realize the proposed scheme. Numerical simulation results prove the feasibility of the strategy.