Optical multi-image encryption scheme with chaotic apertured quaternion fractional Mellin transform

To enhance the encryption quality and the transmission efficiency, an optical compression and encryption scheme for multiple images based on chaotic apertured quaternion fractional Mellin transform (QFrMT) is designed. The apertured optical systems and the quaternions with several imaginary components guarantee our designed scheme harder for the attackers to acquire valuable information. The QFrMT with the chaotic aperture is proposed to eliminate potential insecurity resulting from the known-plaintext attack and the phase-retrieval attack. The quaternion signal containing the main information of the plaintext images is converted into the chaotic apertured QFrMT domain, and then the resulting amplitude is encrypted with the chaotic mask constructed by the truncated phase in the fractional Fourier plane for nonlinear processing and information integrity. The chaos-based non-conventional diffusion is applied to further enhance the robustness against attacks. Extensive experiments results verify the security and efficiency of the presented optical multi-image encryption scheme.