High-flexibility optical encryption via aperture movement.

We present a new method using single-path beam-propagation-based imaging via aperture movement for optical encryption. The aperture is sequentially moved in the transverse domain, and a series of diffraction intensity patterns (i.e., ciphertexts) are correspondingly recorded during optical encryption. An iterative phase retrieval algorithm is applied for the decryption. It is illustrated that the proposed optical security system possesses several significant advantages, such as high flexibility and high security. The proposed optical security system also provides an effective channel to control information assignment and authentication.