A Novel Multi-image Encryption Algorithm Based on the RDFrMT and Cascaded Phase Retrieval.

In this paper, a multi-image encryption method is presented by using the Random Discrete Fractional Mellin Transform (RDFrMT) and the cascaded phase retrieval algorithm (PRA). Firstly, we define the RDFrMT and discuss its properties including nonlinear, multi-parameter, and randomness. Then, based on the RDFrMT, a cascaded multiple-image encryption scheme is proposed. In our algorithm, an image generated by logistic map is transformed to the RDFrMT domain, and the resulting image is fed into the PRA. This nonlinear process makes our cryptosystem robust for potential attacks and ensures its security. Thereafter, the output is cut based on the Hamming distance and the keys are related to multiple input images, which makes our cryptosystem has distinct security level for different images. We repeat the above steps and get a cascaded encryption scheme. Numerical simulations demonstrate the security and feasibility of the proposed scheme.