Optical Information Security Based On Ghost Imaging

Information security plays an important role in this information age.In some places,the eavesdropped information would lead to imponderable loss.If information security technology is used in these places,the eavesdropper could not obtain the real information even if the encoded information is already obtained,and the unwanted loss could be avoided.Optical information security technology becomes more and more important in information security area because of it's high-degree of freedom,strong robustness,parallel processing ability and high speed.Optical image encryption and identification technologies are branchs of optical information security technology.To proposed diversified and higher security optical encryption and identification system,many optical techniques are used in optical security area.In this dissertation,the application of ghost imaging in optical information security area is analyzed,an optical a multiple-image encryption system and an image identification system by using ghost imaging are proposed.An chosen-plaintext attack scheme on part of existing encryption system is also proposed.Numerical simulation are provided to analysis these proposed scheme.The primary works are listed as follows:An optical multiple-image encryption scheme based on ghost imaging is proposed.Different from common multiple-image cryptosystems,the ciphertext of proposed scheme is simply an intensity vector instead of complex amplitude.In encryption process,each plain image is encrypted into an intensity vector by using the computational ghost imaging with a different diffraction distance from source to object.The random phase sequence used to obtain the speckle field is treated as keys.The final ciphertext is generated by superposing all the intensity vectors together.In decryption process,the detector is placed at the different place to obtain the corresponding image.Numerical simulation and optical experiment are both presented to verify the validity of the proposed scheme in practical application.Proposed multiple image encryption system use a series random phase to simulate the pseudo-thermal light and treat these phase masks as keys.Hence the size of keys is very big,which increase the stress of transmitting and managing it.A modified encryption scheme is proposed,which can decrease the size of keys and ensure the security of system at the same time.A chosen-plaintext attack scheme is proposed based on ghost imaging technology.The feasibility and the attack results are analysed by taking the representative optical cryptosystems which combined with linear canonical transform,random phase encoding and random pixel scrambling as example.The plaintexts are chosen as Gaussian random real number matrixes,and the corresponding ciphertexts are regarded as prior knowledge of the proposed attack method.The proposed attack scheme do a analogy between encryption system and ghost imaging system.To establish the reconstruct of the secret plaintext,correlated imaging is employed using known resources.To decrease the number of chosen plaintext-ciphertext pairs,compressive ghost imaging and sinusoidal ghost imaging are employed.In addition,We also consider the possibility of attacking double random phase amplitude encode system,phase-truncated double phase encode system and two of its modified system.An optical image identification system by using incoherent light based on ghost imaging is proposed.The ghost imaging can perform Fourier-space filtering after modify the setup and set some parameters.We proposed an optical image identification system based on this theory result with the help of phase matched filtering theory.Before verify process,the correct image is encoded into the system key and the image to be verified is encoded into the ID card.Using the incoherent light source and after a number of measurement,the resulting ghost imaging is the result of identification.If the ID card is correct,there would appear a correlation peak in it.On the contrary,there would no peak in it.When computational ghost imaging is used,then the proposed system can perform image identification only by a single-pixel detector and very small sampling rate.