Securing color image by using phase-only encoding in Fresnel domains

•The encoded image and main key are in phase-only information.•A random data as main key is located at common path to secure color image.•The physical parameters in encryption system are regarded as the additional keys.

We propose a novel color image hiding scheme with three channels of cascaded Fresnel domain phase-only filtering. The original color image is encoded into three phase masks by using the Gerchberg–Saxton iterative phase retrieval algorithm with another predefined phase key. The individual phase masks are placed in the inputs of the Fresnel domains of the red–green–blue channels and the phase key in the public channel, during the optical retrieval. The physical parameters in the optical system will be regarded as the additional keys for security enhancement. Numerical simulation is performed to test the validity of our scheme.