Secure holographic memory by two-wave encryption method with a photorefractive crystal

Abstract

We propose a new all-optical encryption technique, which is a two-wave encryption method, and discuss security and holographic memory using this technique. Unlike the DRPE method, this technique is characterized by its ability to reduce output intensity for unauthorized memory access, along with the property to output a recorded white-noise image. Thus, the monitoring of output intensity achieves easy detection of unauthorized access. According to our numerical simulation, a particularly significant difference can be found in output intensity, with a correlation coefficient of 20% or under between a key using unauthorized access and a compatible key to find detection sensitivity of unauthorized access. Robustness can be readily improved by increasing key length, and the probability was observed to be 10−6 or under on identifying a randomly generated key with a key length of about 32× 32 for the compatible key, even though the key length is too small. It is shown experimentally that the use of a compatible key reproduced a clear original image, but unauthorized key-based reproduction reduced output strength to approximately 1/20.