Cascade cryptographic key-distribution protocol over a public network based on snapshot compressive ghost imaging

Computational ghost imaging is widely used in classical cryptographic key distribution (CKD) because its measurement and reconstruction are equivalent to the encoding and decoding of signals. Although the measurement efficiency and key-generation rate can be improved by using snapshot compressive ghost-imaging technique, it is still hard to deal with the risk of private key leakage. In this paper, we propose a cascade snapshot CKD protocol over a public network. In each round of communication, multiframe binary block diagrams embedded with cryptographic keys, Arnold transform parameters (derived from the checksum data of recovered images in the previous communication), and users' authentication information are superimposed into one image frame that is measured within a single exposure of an array detector, here the Arnold transformation is applied to randomly disrupt the previously used modulation patterns according to the above parameters, which greatly enhances the nonstealability of private keys and makes the temporary intrusion of a fake identity nowhere to hide. Both simulation and experimental results have demonstrated the feasibility of this protocol and its ability to detect illegal attacks. We believe that the introduction of the cascade idea will accelerate the practicalization process of snapshot CKD.