Real Time Medical Image Encryption Based on Digitial Hologram in Various Optical Domains


 The use of digital hologram (DH) in optical medical images is analyzed in this paper. These analyses are done in various domains of double random phase encoding and it has been proposed. The domains are fractional Fourier, Gyrator, Fractional Hartley and Fresnel. In order to use in real time scheming, this proposal are used many medical images such as MRI Scan, X-ray and mammograms. These medical images are optically explored with the various domains of double random phase encoding. At that time, various encryption areas in double random phase encoding (DRPE) are considered with boosted confidence of security. The encryption and decryption process in various domains makes the complete chart analysis for all kind of medical images which can be used for real time processing. Simulation analysis and results shows the legitimacy and efficiency of proposed scheme.


Introduction
The fast and quick propagation of optical medical image handling schemes delivers numerous gradations of self-determination for safeguarding records, data, or imageries. These can be done for two dimensional (2D) imaging aptitudes, in elevation rapidity, and the parallelisms [1] [2]. Researchers deeply analyzed about double random phase encoding. Javidi [3] initiated this system using Fourier transforms. Many of the researchers started to perform in various transforms such as Fresnel [5][6][7][8], gyrator transforms [9][10][11], fractional Fourier transform [12][13][14][15]. But all these transforms renovates input information into dissimilar mixed spacefrequency domains. But most of the designed cryptosystems are symmetric and they are vulnerable to chosen plaintext attacks, chosen cipher text attacks and known plaintext attacks. In order to overcome these attacks, asymmetric cryptosystem [16][17][18][19][20][21][22] has been designed. Moreover digital holographic [23][24] methods uses a charge coupled device (CCD) camera for straight footage of a hologram must develop obtainable due to the growth of the imaging machinery. Popular the residence of old-fashioned random phase masks, many researchers developed different masks such as SPM( structured phase masks) [25][26][27] and it delivers additional benefit of consuming extra encryption secrets for enlarged confidence. It is usually whole after a Fresnel zone plate (FZP) and a spiral phase plate (SPP). Barrera et al. [27,28] presented a structure phase masks named Toroidal zone plate (TZP). Some other phase masks are Deterministic phase masks [28][29][30]. One another masks is also generated which is called as chaotic structured phase masks can be used in double random phase encoding. Many simulations are performed with respect to real time medical images. All these analysis are based upon digital hologram and it is done in numerous domains which is categorized as Fresnel, fractional Fourier and gyrator transforms.

II. PROPOSED MODULE a. Mathematical Principle
Where B and E is the object wave field and reference field respectively. Complex conjugate is denoted by *. The holograms remain essentially a two dimensional intensity distribution. Supplementary, it is also called as two dimensional or three dimensional distributions can be scrambled by means of visual systems such as double random phase encryption and other direct and indirect optical encrypting procedures. Equation 1 completely denotes the interference patterns at the hologram plane. Now, this can be promoted and administered in numerous Optical transforms (OPT). Some of the OPTs are Fractional Fourier Transforms (FrFT), Fresnel Transforms (FrT) and Gyrator Transforms (GT) to encrypt holograms. The encryption of all hologram created on double random phase encoding will be applied by double consecutive OPTs [4,12,[13][14][15][16][17][18]. Process of doing encryption is given in below equation.
Where 1 2 are the statistically independent two random phase masks.   Figure. 2. The FrFT of order α of an input function ( ) can be indicated as [12][13][14][15], Where = 2 is the angle analogous to the transform order α along the x-axis. The second Optical transform domain is Fresnel transform (FrT). Opto electronic set up is represented in Figure.3. There are two planes called as Input plane and Output plane. is represented as free space propagation distance.
, denotes the Fresnel domain and (λ, z) are considered as parameters. ℎ , ( , , , ) is given in equation 7, The third optical transform domain is gyrator transform. The complete representation of optical set up of gyrator transform is shown in Figure. 4. GT is called as gyrator transform and L1 is the combination of cylindrical lens.

b. Encryption and Decryption
Encryption and decryption of our proposed system is given below. Before starting the encryption and decryption, this proposed system considered medical images such as MRI Scan, lung cancer, retina, skin cancer and breast cancer. As a sample, original spectrum, high pass spectrum and high pass image for MRI scan is shown in figure 5.
After this transformation, the absolute portion from equation 23 is extracted and used in below equation, . * exp ( * 3)); Apply the inverse optical transformation to the above equation,

c. Performance Analysis
The performance analysis has been performed such as Mean Square Error(MSE), Peak Signal-to -Noise Ratio(PSNR), Relative Error(RE). 1. Mean Square Error(MSE) [29][30][31]: MSE has been calculated for the proposed model, using the given equation Where ( , ) and ′ ( , ) denotes the plain image and decrypted image respectively.
shows the size of the image.

Peak Signal To Noise Ratio (PSNR)
PSNR has been calculated using the given formula [29][30][31], Where ( , ) and ′ ( , ) denotes the plain image and decrypted image respectively. shows the size of the image.
shows the size of the image [29][30][31]. Table 1. Represents the values for the proposed model.  The noise analysis has been made for the proposed model [29][30][31]. The plot is made between MSE and the noise factor. If the noises are increases in the system, of course the MSE value also gets increased. For all the three medical images, plot has been drawn. For all the three medical images, noise plot has been made MSE Vs. Noise factor and it is shown in Figure. 10.

e. Sensitivity Analysis
The sensitivity analysis has been carried out for out proposed model. It has been done for all the OPT's such as fractional Fourier, Fresnel and gyrator transforms.

Fractional Fourier transforms:
As discussed in the mathematical background, it needs two security parameters ( , ). In the proposed model, these two values are fixed with = = 0.5. When Digital hologram is combined with double random phase encoding and it had been proposed for medical images. All the analysis had been performed with various transforms such as fractional Fourier, gyrator and Fresnel. In instruction to use in real time devious, this suggestion are used for many medical images such as MRI Scan, X-ray, skin cancer and mammograms. These medical images are optically discovered with the various domains of double random phase encoding. At that time, various encryption areas in double random phase encoding (DRPE) are considered with advanced self-confidence of security.