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Simultaneous Encryption of Two Grayscale Images Using Digital Holographic Processing and Performance Analysis
Abstract
The robustness of simultaneous encryption of two
grayscale 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 by
incorporating 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 are
real 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.
Keywords
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