Research On Image Encryption Algorithm Based On Optical Information Processing Technique

With the popularity of internet and the development of communication technology,Data information is facing growing chance to be stolen,illegally copied and disseminated.Image,as the main carrier of information,is also facing increasingly serious security problems.In recent years,more and more researchers studying on image security are attracted by optical information processing techniques due to their strengths of multi-dimension,high parallelism and more degrees of free in the form of different parameters such as wavelength,polarization,focal length and distance between lenses.Therefore,some kinds of image encryption schemes based on optical information processing technique are studied in this thesis,in which the research work can be mainly summarized as follows:First,an asymmetric double-image encryption scheme based on cascaded discrete fractional random transform is proposed.Two new components are obtained by subsequent operations such as combination,permutation and decomposition on two plain images,where one is decomposed into two phase masks and served as encryption keys,the other one is encrypted to form the ciphertext by using caseded DFrRTs.The phase functions of the transformed results are extracted by using the phase truncation technique and exploited as decryption keys.Simulation results show the proposed scheme has high resistance against common attacks such as noise attack,occlusion attack,statistical attack and chosen plaintext attack.Second,a new discrete fractional transform named as the discrete multiple-parameter fractional angular transform(DMPFAT)is presented and employed in the double-image encryption scheme.The proposed encryption scheme has an obvious advantage that no phase mask is used as the private key,which is convenient to management such as the storage and transmission of key.Due to high sentivity of transform parameters such as fractional order and vector,the security of the proposed scheme is enhanced further by using these parameters as private keys.Additionally,a secure double-image sharing scheme is proposed under the framework of Shamir's three-pass protocol by making use of the linear additvity property of DMPFAT.The proposed sharing scheme is verified by simulation results,which not only has resistance against the conventional attacks such as noise attack,occlusion attack and statistical attack,but also has high robustness against main-in-the-middle attack and the type attack.Finally,an image encryption scheme using conventional integral imaging technique is improved in the fractional Fourier transform(FrFT)domain,in which the computational integral imaging(CII)is deployed to obtain the element image array(EIA)of the plaintext image.The EIA image is scrambled with the help of the random sequence engendered by using Logistic map function and then modulated with a randomly generated phase mask.The resultant complex function is encrypted to the ciphertext by usng the FrFT.The feasibility and effectiveness of the proposed scheme is verified with simulation results.Meanwhile,the proposed scheme has high robustness against different attacks such as noise attack and occlusion attack due to data redundancy property of EIA.