| Abstract:Geological data is the embodiment and historical records of geological work achievements, is indispensable precious wealth for national economic construction and scientific development. In recent years, with the rapid development of global social economy and the digital technology, the storage, service and management mode also changed greatly. The provincial geological archives across the country have launched a large-scale digital work of geological data. At present, in view of the need to identify the authenticity of digital geological data in the process of submission and distribution, the Development Research Center of China Geological Survey Bureau organized the application of digital watermarking technology in intellectual property management of geological data. However the application of digital watermarking this technology is limited greatly, because it requires the content providers to pre-process the images and provide authentication information actively. Due to the requirements of application and limitations of existing technology, based on blind detection technology this thesis proposes digital geological data detection technology, which is a technology of detecting image authenticity, integrity and primitiveness without relying on digital signature or watermark information and with broad prospect.Aimed at the authenticity detection of JPEG geological image, this paper makes an in-depth research on the related key techniques on the basis of summarizing and analyzing the blind detection methods that exist from the tampering scenarios and image format, and proposed three passive detection methods for JPEG geological image, and tested on different kinds of digital geological image. The effectiveness of the proposed methods is verified by experimental comparison and analysis. The main contents and innovations are as follows:(1) A copy-move forgery detection method for JPEG geological images based on SURF algorithm is proposed. Aiming at the shortcomings of the traditional copy-move forgery block-matching detection methods, including large computational quantity, can't distinguish the tampered region from the copy-move regions, and the inaccuracy of tampered region location, a copy-move forgery detection method for JPEG geological images is proposed based on SURF algorithm. Firstly, the SURF algorithm is applied to extract keypoints and descriptor vectors of the given image. Secondly, match the detected keypoints by computing the Euclidean distance of their descriptor vectors, and locate the copy-move regions. Then, the blocking artifact characteristics matrix factor (FBACM) is proposed base on JPEG compression, and finally, the tampered region is located according to the JPEG BACM factor. Experimental results show that, the proposed method has considerable advantages over traditional DCT and PCA block-matching methods in efficiency, robustness and accuracy.(2) A passive tampering detection for JPEG geological image based on ASAD is Proposed. The commonly used Inpainting and splicing tampering techniques can be classified according to the format which the tampered image is saved in after tampering. A passive tampering detection for JPEG geological image is proposed based on ASAD by introducing the simulation and feasibility analysis for different tampering schemes. The tampered region is detected by computing the averaged sum of absolute difference (ASAD) images between the tampered image and a resaved JPEG compressed image at different quality factors. In addition, the discussion and analysis of the related parameters selection is presented at the experiment segment. Experimental results show that, the proposed method works for inpainting and splicing tampering techniques when the tampered image is saved in an uncompressed format or in JPEG compressed format, and the robustness and the tampered region location accuracy of the proposed method are higher than those of BAG extraction method.(3) A passive tampering detection for JPEG geological image based on the characteristic of the first digits is proposed. Aiming at the first digits'probability distribution of the DCT and singly compressed JPEG coefficients, a generalized Benford's law which follows the distribution of singly compressed JPEG coefficients is studied. According to the generalized Benford's law, the probability distribution of JPEG coefficients obtained by different compression schemes analyze. On the basis of this, a passive tampering detection for JPEG geological image based on the characteristic of the first digits is proposed. In the algorithm, the tampered region detection can be treated as a two-class pattern recognition problem. Firstly, the sub-images are extracted from the to-be detected image. Then, for each sub-image, calculate its first digits' probability distribution of JPEG coefficients of individual AC modes as feature vectors, and support vector machine (SVM) is applied to detect and locate the tampered region. Experimental results show that, the proposed method can effectively detect three kinds of commonly used tampering schemes for digital geological images, including "JPEG+uncompressed","JPEG+JPEG" and "JPEG+Inpainting", and the performance of the proposed method is obviously better than that of SAD and BPPM algorithms.In conclusion, this thesis mainly focuses on the blind forensics research of identifying the authenticity of digital geological data. Some achievements have been made in theory and application. These achievements will provide technical guarantee and support for safe, effective, practical and services of digital geological data. |
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