Overview of optical security systems based on double random phase encryption,analyticalmethods and holographic memory

In the present Teview paper, an overview has been presented of the different optical encryption schemes which have potential to keep the information protected so as to provide secure transmission and storage, and to make accessible the original data to an authorized user. Cryptanalysis of the double random phase encryption (DRPE) scheme provides an insight into its weaknesses, and reasons due to which different types of attacks are able to breach the security of the scheme. Some strategies to circumvent the problems related to the vulnerabilities of the DRPE schemes have been described with an emphasis on making the scheme impulse attack-free. A succinct survey of the iterative algorithm based encryption schemes brings into focus the fact that these schemes are slow due the iterative nature of phase masks generation. Removal of an inherent silhouette problem in the analytically generated phase-only masks with jigsaw transformation has been discussed. A simple alternative method for the optical implementation using a single spatial light modulator has also been implemented. A brief discussion of the holographic security systems has been presented, and enhancement in the security by use of convergent random illumination has been discussed.