Non-interferometric key recording applied to a joint transform cryptosystem

In this Letter, we propose an opto-digital cryptosystem based on the joint transform correlator architecture without the need for a reference beam, phase-shifting techniques, or an additional window in the input plane. In this system, only two intensity recordings are necessary: the intensity of the key Fourier transform, and the joint power spectrum between the key and an arbitrary object in contact with a random phase mask. Combining them with the knowledge of their respective input modules, we implement a modified Gerchberg-Saxton algorithm to recover the phase associated with the encryption key. The validity of our approach is demonstrated by computer simulations and experimental results.