Multiple-image encryption by space multiplexing based on vector quantization and interference

Abstract

A new multiple-image encryption scheme utilizing vector quantization and interference has been proposed. Firstly, the quick response codes engendered from plain images are converted into index images via vector quantization encoding and then integrated into an interim distribution using space multiplexing. Next, the interference is invoked in the fractional Fourier transform domain for encrypting the interim distribution into a real-valued ciphertext as well as a secret key. Parameters, such as the order of the fractional Fourier transform, are able to enhance the key space of the cryptosystem to assure a high level of security. Even when the ciphertext is severely disturbed by occlusion and noise, the plain images can be read out without any information loss by scanning the decrypted codes with a mobile device. In addition, the affection of cross-talk existing in the multiple-image encryption schemes can be efficiently avoided. To our knowledge, it is the first time vector quantization is applied to integrate multiple images in the field of image encryption based on interference, which can improve the robustness against common attacks. The feasibility and effectiveness of this scheme have been demonstrated by numerical simulations.