Attack on Optical Double Random Phase Encryption Based on the Principle of Ptychographical Imaging**Supported by the National Natural Science Foundation of China under Grant Nos 61575197 and 61307018, the K. C. Wong Education Foundation, the President Fund of University of Chinese Academy of Sciences, and the Fusion Funds of Research and Education of Chinese Academy of Sciences.

Abstract

The principle of ptychography is applied in known plain text attack on the double random phase encoding (DRPE) system. We find that with several pairs of plain texts and cipher texts, the model of attack on DRPE can be converted to the model of ptychographical imaging. Owing to the inherent merits of the ptychographical imaging, the DRPE system can be breached totally in a fast and nearly perfect way, which is unavailable for currently existing attack methods. Further, since the decryption keys can be seen as an object to be imaged from the perspective of imaging, the ptychographical technique may be a kind of new direction to further analysis of the security of other encryption systems based on double random keys.