A novel image encryption method is proposed by utilizing random phase encoding in the fractional Fourier domain to encrypt two images into one encrypted image with stationary white distribution.By applying the correct keys which consist of the fractional orders,the random phase masks and the pixel scrambling operator,the two primary images can be recovered without cross-talk.The decryption process is robust against the loss of data.The phase-based image with a larger key space is more sensitive to keys and disturbances than the amplitude-based image.The pixel scrambling operation improves the quality of the decrypted image when noise perturbation occurs.The novel approach is verified by simulations.