Optical image encryption based on wavelet packet transform and fractional Fourier transform
Han Zhou · Journal of Optoelectronics·laser · 2013
A novel method for the optical image encryption is presented,which is based on the wavelet packet transform(WPT) and fractional Fourier transform(FRFT).The idea of combining WPT with FRFT comes from the study of properties of them.Images can be decomposed by wavelet packet transform.With the increase in the order of WPT,the image will be decomposed into more parts,of which each contains the essential information.Based on the good property of WPT and the flexibility of FRFT,the method implicates encryption and decryption of the image and produces many keys,consisting of double random phase masks,the order of WPT and the order of FRFT.Meanwhile,the selected-image-encryption in wavlet domain is realized in this paper,which varies the patterns of encryption.The method improves the security,and the ability of resisting malicious attacks is also enhanced.The encryption and decryption are implicated by numerical simulation.The result of the simulation provides the requirement for analyzing the properties of encryption and decryption.The feasibility and simplicity of the method are verified by numerical simulation,and a simple optical implication of the method is also proposed.Based on the numerical simulation and theroy analysis,it can be confluded that the method for the optical image encryption is novel and effective.