Multiple Image Encryption with Fractional Hartley Transform and Robust Chaotic Mapping

In this paper, we present a simple yet highly robust mechanism for multiple image encryption with optical transformation. A fractional order Hartley transform framework along with secret reversible integer transform (RIT) is used to decorrelate the images. The selection of fractional orders is based on a robust chaotic mapping. Optical transforms support fast and parallel processing but have limitation in digital implementation due to complex coefficients. We present a paradigm where complexity is completely eliminated at each security level to overcome the need of time consuming phase retrieval algorithms. The amalgamation of chaos further make it a highly sensitive and secure technique. This method gives optimum results with almost uniform histogram and lossless recovery of data which is otherwise limitation of optical transforms whose energy is concentrated at the center.