Phase retrieval algorithm for optical information security

As a typical technology for optical encryption,phase retrieval algorithms have been widely used in optical information encryption and authentication systems.This paper presents three applications of two-dimensional(2D)phase retrieval for optical encryption and authentication:first,a hierarchical image encryption system,by which multiple images can be hidden into cascaded multiple phase masks;second,a multilevel image authentication system,which combines(t,n)threshold secret sharing(both t and n are positive integers,and t≤n)and phase retrieval,and provides both high-level and low-level authentication;and finally,a hierarchical multilevel authentication system that combines the secret sharing scheme based on basic vector operations and the phase retrieval,by which more certification images can be encoded into multiple cascaded phase masks of different hierarchical levels.These three phase retrieval algorithms can effectively illustrate phase-retrievalbased optical information security.The principles and features of each phase-retrieval-based optical security method are analyzed and discussed.It is hoped that this review will illustrate the current development of phase retrieval algorithms for optical information security and will also shed light on the future development of phase retrieval algorithms for optical information security.