A phase-key duplication technique is introduced. The phase-key in the doudle random-phase encoding system is recorded as digital holograms for this purpose. Therefore,the user who remotely access the encrypted data can recover the original image with the phase-key reconstructed by use of a corresponding phase-shifting algorithm from the recorded holograms. We analyze the influence of the noise in the COD camera on the recording process to the reconstruction of the phase-key. In addition,we also present a possible application of the technique of phase-key duplication based on digital holography.