Study On Reversible Data Hiding Algorithm For Encrypted Medical Image

The Digital Imaging and Communications in Medical(DICOM) is the standard for formatting the digital medical images displaying, exchanging and storing in communication network. DICOM standard simplifies the exchange of medical image information, and further promotes the digital process of telemedicine. With the continuous development of computer science and communication technology, the popularity of DICOM standard and the implementation of telemedicine, confidentiality and authentication protection of medical image are becoming more and more important.Recently, various types of security technology are proposed to improve the security of the information transmission, cryptography and information hiding technology are the two most important branches. Cryptography is to hide the content of plain information, and the information hiding technology makes the existence of information invisible to the illegal users. In practice, the combination of encryption and data hiding technology usually are required to improve the data security, which provides not only confidentiality protection, but also integrity protection. Therefore, with the development of telemedicine technology, research on reversible data hiding algorithm based on encrypted medical image is important, significance and practical value.The works of this article are as follows:Firstly, research and analysis on the existing algorithms of medical image compression, cryptography and data hiding, so as to design the reversible data hiding algorithm based on encrypted medical images.Secondly, in order to implement reversibility of data hiding technology and improve the information embedding rate, a reversible data hiding algorithm for encrypted images based on a partial compression is proposed by using of edge detection, run length coding, chaotic encryption and LSB substitution. At first, the edge information of an image is detected by SUSAN algorithm, and the image is reconstructed after compressing boundary portion by means of run length coding(RLC). Then the image is encrypted using chaotic algorithm and the LSB replacement method is used to embed the watermark in the encrypted image. In the receiving side, there are three operations to choose according to the obtained keys for the receiver. The simulations on MATLAB indicate that the algorithm has a high embedding capacity, and the operating sequence of decryption and watermark extraction is flexible.Thirdly, combination of RLC, scrambling encryption and histogram modification, a reversible data hiding algorithm for encrypted images based on an overall compression is proposed. At first, the image is decomposed into 8 independent bit-planes, the higher four bit-plans are compressed using RLC and the image is reconstructed. Then the image is scrambled according to the sequence which generated by Logistic chaotic map. Finally, information is embedded into the encrypted image by using histogram modification. The algorithm is suitable for all kinds of digital images(for example the images which cannot find zero point), the peak point and the zero point is stored in the reserved room, so there is no need to send the peak point and the zero point, and the operation sequence at the receiving end is flexible.Finally, we summarize the article and indicate the future research of data hiding for encrypted images.