Enhanced Image Protection Using Discrete Fractional Fourier Domain and Dual Random Phase Encoding

Abstract

In the digital era, secure image transmission is critical for applications ranging from medical imaging to military surveillance. Encryption is one of the well-known techniques to provide security in the transmission of multimedia content over the internet and wireless networks. There is use of image in all the areas, so its security is of great concern nowadays. In this paper, we propose a novel method of image encryption using discrete fractional Fourier transform (DFrFT) using an exponential random phase mask. The proposed method employs a two-phase masking approach, where the input image is first modulated with a random phase mask in the spatial domain and subsequently transformed using the DFrFT with tunable fractional orders. A second random phase mask is applied in the fractional frequency domain to further obscure image content. This technique makes it almost impossible to retrieve the image without using both the right keys. The combination of multidimensional DFrFT and random phase modulation significantly increases the key space and sensitivity to initial conditions, making brute-force and plaintext attacks computationally infeasible. Experimental results validate the robustness of the proposed method in terms of Peak Signal-to-Noise Ratio (PSNR) of maximum 42.02 dB, keyspace analysis for security, computational complexity same as FrFT, processing time 2.8654 seconds and mean square error -1.5735 dB obtained.