Research On 2D Image And 3D Scene Encryption Based On Computer Generated Hologram And Chaos

Chaotic cryptography and optical information security technology are the key research directions in the field of information encryption,widely used in the design of image encryption algorithm,but mainly for gray images,there are few significant results about 3D scene encryption.The research shows that the digital holography(or CGH)based on light wave diffraction and interference calculation has the advantage of encryption.It can process RGB channel components of color image as a whole through spatial superposition and spectrum separation,and realize dimensional compression of 3D information through 2D computer generated hologram.It has the advantages of easier storage,transmission and reconstruction of real and virtual 3D scenes.The hologram is encrypted into a meaningless white noise image by replacing and diffusing the pixel value of the hologram by chaotic system,it helps to enhance the ability of ciphertext to resist statistical attack and ciphertext only attack.The nonlinear operation of chaotic encryption also helps to resist the chosen plaintext attack,and the diffusion mechanism enhances the sensitivity of ciphertext to plaintext changes,which further improves the security.In view of this,combined with computer-generated hologram and the theory of chaotic encryption,this dissertation studies the security problems existing in the storage and transmission process of existing color images and 3D scene information,and proposes new encryption schemes.The main contents are as follows:1.This dissertation briefly introduces the basic principle of generating and reconstructing CGH of two-dimensional and three-dimensional objects.Secondly,it introduces the modern image encryption technology,mainly introduces the encryption based on Holography and chaotic system.2.A color image encryption scheme based on the combination of Fourier holography and chaotic system is proposed.The scheme encrypts and superimposes the color image into a gray-scale CGH through multiplex the incident angle,wavelength,diffraction distance and other parameters in the generation process of CGH,and then encrypts the CGH for the second time through Logistic chaotic system.Then,through numerical simulation,the feasibility of the proposed method is analyzed,and it is verified that the method has little loss of color and gray information for the original color image,and the reproduction effect is good.The security of the encryption method is evaluated by analyzing the correlation of adjacent pixels,key sensitivity and information entropy.3.Aiming at the disadvantage that the volume of ciphertext or key becomes larger after the three-dimensional information encryption is not conducive to storage and data transmission,a 3D scene encryption scheme based on the combination of CGH and chaos system is proposed.The scheme encodes the 3D scene into a CGH by point source method,then encrypts the hologram into three phase-only holograms by using 3D GS algorithm,and finally obtains the final encryption result by using Lorenz hyper chaotic system and vector operation.The feasibility and safety of the proposed method are verified by numerical simulation.