Non-linear Cryptosystem for Image Encryption Using Radial Hilbert Mask in Fractional Fourier Transform Domain
An asymmetric image encryption scheme has been proposed in the fractional Fourier transform (FRT) domain, using a radial Hilbert mask in the input plane and a random phase mask based in the frequency plane. The use of a radial Hilbert mask provides an addition of extra encryption parameter along with the asymmetric scheme which is non-linear where the encryption and decryption keys are different. The encrypted image resulting from the application of FRT is attenuated by a factor and combined with the asymmetric scheme to provide an encrypted image. The decryption process is the reverse of the encryption. The designed scheme has been implemented digitally using MATLAB R2014a (126.96.36.1992). By analysing the decryption results using input images the strength and efficacy of the proposed scheme has been established. The performance assessment of the method has been evaluated in terms of peak signal-to-noise ratio, mean-squared-error (MSE). The proposed scheme provides increased security.