Double random phase encoding (DRPE) is a typical optical encryption technique, in which the cipher key is allowed to include redundancy between encryption and decryption. It has been shown that phase-only DRPE has the robust to known-plaintext attacks using a phase retrieval algorithm. In addition, it has been also shown that phase only DRPE can decrypt the encrypted image successfully with the singular key that is completely different from the encryption key. In this study, we analyzed the distribution of the key-space in the phase-only DRPE by means of calculating the Euclidean distance between the decryption key and the encryption key and counting the number of the correct decryption keys. As a result of the experiments, we confirmed that the distribution property of the correct keys in the phase-only DRPE is significantly different from the one in the conventional DRPE.
© 2010 Optical Society of AmericaPDF Article