Asymmetric double-image encryption based on chaotic random phase encoding

Abstract

An asymmetric double-image encryption scheme based on chaotic random phase encoding (CRPE) is proposed. In this proposed encryption scheme, two grayscale images to be encrypted are first Fresnel transformed and combined into a complex image. Then, the amplitude and phase components are obtained by conducting phase–amplitude truncation on the complex image. Finally, the amplitude component is again Fresnel transformed and encrypted into a noise-like pattern by the CRPE in the Fresnel domain. Since the initial values and control parameters of the chaotic map can replace the random phase masks to serve as secret keys, the management and transmission of secret keys will become more convenient in the proposed encryption scheme. Furthermore, the Fresnel transform parameters and phase keys derived from the complex image’s phase component can also act as secret keys during the decryption process. Numerical simulations have demonstrated the feasibility, security, and robustness of the proposed encryption scheme.