Research On Image Robustness Encryption Based On Compressive Sensing And Chaos

The 21 st century is the continuous development and progress era of the information and network technology.This brings great convenience for us;at the same time,how to ensure the information security has also become the focus of the whole society.Digital information is widely distributed,stored and processed on the Internet,which penetrates into all aspects of our production and lives.Digital image,as the most intuitive information carrier,is different from the ordinary text,which has its own unique characteristics.So it is very important to ensure the image security in vulnerable and unsafe transmission network.However,the traditional encryption algorithm generally focuses on the security but ignores the robustness.When the encrypted image is tampered or attacked in an insecure channel,it is still valuable in some applications if the quality of the restored original image can be acceptable to some extent.Therefore,to ensure that the receiver can still restore the original image information when he receives the damaged encrypted image,it is necessary to study the robustness encryption algorithm against various attacks.Chaos and compressive sensing(CS)have brought new opportunities for the images robustness encryption algorithm because of their good characteristics.This thesis focuses on the images robustness encryption based on CS and chaos.The main work of this thesis is as follows:(1)By researching the basis of chaos theory,CS theory and image encryption algorithm,we have a systematic understanding on how to design a robust encryption algorithm based on chaos and CS.By comparing the advantages and disadvantages of other algorithms,the main characteristics of robustness encryption algorithms are studied systematically,which lays the foundation for the follow-up research.(2)A robust image encryption algorithm based on CS and chaos is proposed.The proposed algorithm overcomes the shortcomings of the traditional algorithm in which the decryption scheme cannot completely restore the original image or needs high cost of hardware and software to realize when the encrypted image is tampered.The attacked encrypted image can be restored by using the reconstruction features of CS.The original image is transformed by the discrete wavelet to the sparse coefficient matrix.Then the measurement matrix is generated by using the chaotic map,and the sparse coefficient is measured to obtain the measurements.And the measurements are quantified to integer values and encrypted based on chaotic map.Finally,we can get the encrypted data.Experiments show that the proposed algorithm can ensure the security of the image and good robustness.(3)A multi-focus image fusion and robust encryption algorithm is proposed to reduce data transmission volume and resist various channel attacks.Firstly,multi-focus image is fused by the fusion algorithm based on wavelet decomposition that can generate complete scene images and optimize the perception of the human eye.Secondly,the fused images are sparsely represented with DCT and sampled with structurally random matrix(SRM),which reduces the data volume and realizes the initial encryption.Then the obtained measurements are further encrypted to resist noise and crop attack through combining permutation and diffusion stages.At the receiver,the cipher images transmitted through insecure channel can be jointly decrypted and reconstructed.Simulation results demonstrate the security and robustness of the proposed scheme.