Securing Color Information Based on CEDPM Keys

In this paper, a novel approach to generating keys for securing color information by combining discrete wavelet transform (DWT) in conjunction with chaotic functions is presented. This procedure is based on chaotic sequences derived using initial conditions and control parameters of the Logistic map function, which are utilized to decompose in different frequency subbands by applying the DWT. These subbands construct the chaotic encoded directional phase masks (CEDPM) keys. To investigate the potential applications of the CEDPM keys, a nonlinear optical cryptosystem for securing color images has been developed. The color image to be encoded in this study is first separated into three color planes such as red (R), green (G), and blue (B) which are transformed into the phase function using a modified phase retrieval algorithm. Subsequently, for R, G, and B color planes in the encoding procedure, the obtained CEDPM keys are employed, correspondingly. This procedure helps to facilitate the creation of a real-value ciphertext for the color channels R, G, and B. These encrypted images, which correspond to the color channels R, G, and B, are positioned at the horizontal, vertical, and diagonal subbands to combine with low-frequency subbands. After that, inverse wavelet operations are carried out to produce a single covered image. This technique strengthens the system's security by adding an additional layer. The efficacy of the color encryption approaches is confirmed using computer simulations. The results and analysis show that the proposed scheme performs satisfactorily in protecting color image components compared to the other techniques in this area.