Study On The Application Of Multimode Fiber Specklegram Based Compressive Sensing In Optical Image Encryption

With the rapid development of internet technology,the research on the efficiency and security of data transmission has become an important research area.As one of the main objects transmitted on the network,image information has a large capacity of data and faces a high security risk.Therefore,compression and encryption of image information has become an effective measure to solve this problem.Because of the advantages of optical information security technology,the encryption of image information has also become one of the important research contents in the field of optical information security.A novel method of optical image compression and encryption is proposed in this paper,which combines the technology of compressive sensing(CS)with the technology of double random phase encoding(DRPE).The specklegrams obtained from the facet of multimode fiber are used as the measurement matrix in the process of CS,and CS completes the compression and first-stage encryption of image information,in which the specklegram measurement matrix functions as the first-stage secret key.Then the technology of double random phase coding continues to complete the second-stage encryption.The main achievements in this paper are as follows:(1)The theoretical analysis of the mode excitation of a multimode fiber with offset launching is carried out.Specklegrams obtained under different experimental conditions were collected,and the randomness of the specklegrams was analyzed.The digital image processing technology was then used to dispose the specklegrams to construct the measurement matrix required in the CS process.(2)The theory related with compressive sensing and double random phase coding were briefly introduced.The feasibility of the combination of compressive sensing and double random phase coding for encryption and decryption was verified.Compared with the traditional measurement matrix in compressive sensing,and the measurement matrix based on the specklegrams shows superiority in the final reconstruction effect,which shows its good potential in the image compression and encryption in optical domain.(3)When the measurement matrix based on a single specklegram and multiple specklegrams are used respectively,the performances of the proposed method to resist attacks such as statistical analysis,noise interference,and cropping attacks are analyzed.The sensitivity of the key and the size of the key space are also discussed.Since the different specklegrams can be easily obtained as the first-stage key under different working wavelengths,a large key space could be obtained when we combine the CS with double random phase coding.When more specklegram measurement matrices are adopted,the key space is larger,and the security is higher.Then a better final image reconstruction effect could be realized.