Novel four random phase encoding and 1D log-cosine-tent chaotic map for multi-image compression-encryption

Abstract In multi-image encryption scenarios, the discrete wavelet transform (DWT) is commonly used to improve the efficiency of compression and encryption. However, it inevitably loses high-frequency details during processing, leading to a decline in the quality of the decrypted images. To overcome these limitations, we propose a one-dimensional log-cos-tent chaotic map (1D-LCTM) characterized with an extented chaotic range. Building upon this foundation and integrating the 1D-LCTM with a Gaussian chaotic aperture fractional Fourier transform filter bank (GCAFrFT-FB), we have developed an advanced four-random-phase encoding (FRPE) algorithm for multi-image encryption. In our method, the high-frequency components generated by DWT are mapped into two sets of random phases, which are then used to encrypt the low-frequency components. The GCAFrFT-FB generates two additional random phases that enhance the system’s sensitivity to optical parameters such as wavelength and fractional order. Finally, experimental results demontablestrate that our method not only fully exploits the high-frequency information to improve decryption quality but also markedly strengthens the security of the algorithm.