Simultaneous Encryption of Two Grayscale Images Using Digital Holographic Processing and Performance Analysis

The robustness of simultaneous encryption of two gray scale images using digital holographic principle has been studied in this paper. Digital holography can process and retrieve complex information i.e. both amplitude and phase information. The present paper explores this possibility for simultaneous encryption of two gray scale images by encoding them in amplitude and phase of the input image respectively. The security of information is ensured byincorporating double random phase encoding in the Fresnel domain or free space propagation domain. This results in to complex encrypted image. When such encoded complex information is sensed by conventional method using a sensor, inherently the phase information will be lost. Therefore the encrypted information should be recorded interferometrically. We employ digital holographic method for recording and reconstructing the complex encrypted image. The resulting inteferograms or holograms detected by a CCD sensor arereal valued images and numerically processed to retrieve the complex encrypted information. Digital holography with two intensity measurements is utilized for this purpose. This method is helpful for retrieving dc and twin image free original information reconstruction.After retrieving the complex encrypted image from the recorded two in-line digital holograms, the reverse process is exercised to retrieve the original decrypted complex image which contains two independent gray scale images those we encoded in amplitude and phase respectively. The robustness of the method is analyzed by computing the mean square error between original input and decrypted images for various set of input images. The computational study performed in this paper shows the proof of concept of the proposed method.