Optical image encryption with silhouette removal based on interference and phase blend processing

Security enhancement of color image cryptosystem by optical interference principle and spiral phase encoding

“…If E 0 r x; y E r x; y − S r 3 x; y represents the interference pattern distribution of S r 1 x; y and S r 2 x; y, then the phase information of E r x; y is not preserved in E 0 r x; y due to nonexistence of S r 3 x; y [33]. Therefore, two SPOMs S r 1 x; y and S r 2 x; y can be analytically obtained from E 0 r x; y.…”

“…He eliminated the silhouette problem completely by encoding the original image into three POMs, one with random phase distribution and generating the other two POMs analytically. He also proposed a linear phase-blend technique to recombine the phase angle values of the three POMs through an orthogonal transform matrix [33]. The transform matrix is determined by a random angle distribution, which provides as an additional key for further enhancement of the security level.…”

Optical interference-based image encryption using circular harmonic expansion and spherical illumination in gyrator transform domain

“…One advantage of this proposal over the previous works is the center-symmetric configuration of the ciphertext, which can relax the optical alignment during the interference procedure. Moreover, the location randomness of expansion center of CHCs provides more freedom and key space to protect the secret information than the earlier works [17,20,21].…”

“…One cannot discern any silhouette pattern that reveal secret information in these noise-like images (RE¼0.6826, RE ¼ 0.7403; MSE ¼ 1.07 10 4 × , MSE ¼1.17 10 4 × ), which is mainly due to the random phase modulation and off-axis CHC expansion. Like the previous schemes [17,20,21] that are devised to remove the silhouette problem during the generation of POMs (or ciphertexts), in the encryption procedures of the proposed scheme, the phase information of inverse GT spectrum m x y ( , ) 1 1 , the main cause of the silhouette problem, is separated randomly through the random phase modulation (Eq. (4)) and decomposition of off-axis CHCs (Eq.…”

“…However, most of them require time-consuming computation for post processing or a greater number of POMs [18,19]. With the expectation to thoroughly resolve this problem at the source, two different triple-POM based methods have been reported recently, which do not need any time-consuming digital computation or post processing of POMs [17,20]. Furthermore, some IBE schemes have been devised for multiple-image or color image encryption by combining with polarized light encoding [21], POM multiplexing [22], position multiplexing [23] and phase-only encoding techniques [24].…”