Security analysis of a cryptosystem based on nonlinear PTFT

In this paper, we analyze the security of a cryptosystem based on the nonlinear phase truncated Fourier transform (PTFT). In the cryptosystem under investigation, a nonlinear factor is added to the conventional PTFT method to enhance the security. Nonlinearity is generated using a random complex distribution, which is added during the encryption process. In our analysis, we observed that the nonlinearity factor is not very robust, and the nonlinear PTFT architecture is still vulnerable. The security of the nonlinear PTFT-based cryptosystem is analyzed, and two modified attacks, i.e., the specific attack and the alternative iterative attack, are proposed to break the cryptosystem. The cryptoanalysis results of nonlinear PTFT have been validated with “Cameraman” and “Binary” grayscale images. The simulation results validate that the original plaintext can be retrieved successfully using the proposed modified attacks. The effectiveness of proposed attack algorithms is also validated by calculating the mean-square-error, mesh plot, and histogram analysis.