A Collusion-Resistant Watermarking Scheme for Digital Elevation Models

  • 林 政毅

Student thesis: Master's Thesis


The thesis provides a practical scheme for the application in DEM transaction tracking which has the task different from application of DEM copyright protection The significant difference of the task is the resistance to collusion attacks An idea of independent and identically distributed (i i d ) Gaussian random vectors which has robustness against not only common signal processes but also collusions attacks is implemented in the thesis and the Security of the proposed scheme is evaluated by the probability of detection and probability of false positive The other task a common issue of watermarking schemes is the trade-off among the Imperceptibility Fidelity Robustness and Security To balance the trade-off the regulation of accuracy requirement for DEM generated in 1/1000 topographic mapping is developed and a cubic spline interpolation is implemented to generate the smooth and rational Human Visual System (HVS) masking called fidelity mask The differences between original DEMs and marked DEMs are measured to evaluate the fidelity and they are examined in multidimensional evaluations for the quality of DEMs and their applicability The Imperceptibility is evaluated by the Peak Signal Noise Ratio (PSNR) contours images of elevation and gradient On the other hand the experiments for Robustness including random noise mean filter medium filter clipping rounding down elevation shifting and scaling are executed especially elevation shifting which is an elevation transformation from the orthometric height to ellipsoidal height DEMs are classified into plain basin tableland hill and mountain according to its elevation and average of slope After classifying the 8 experimental DEMs which are diverse comprehensive and representative are selected from all 6326 DEMs On the basis of the experiments of DEMs containing Fidelity Imperceptibility Robustness and Security the research can be concluded: (1) The proposed scheme has robustness against common signal processes to DEMs (2) The proposed scheme is secure against the average collusion attack and complex collusion attack (3) The watermarks cannot be perceived by human eyes in the marked contours elevation and gradient images (4) The results of fidelity are supported by multidimensional evaluations The major contribution of the thesis is the proposed watermarking scheme utilizing i i d Gaussian random vectors proposed by Cox et al in 1997 is genuinely resistant to average collusion attack for DEMs in transaction tracking
Date of Award2018 Aug 1
Original languageEnglish
SupervisorJaan-Rong Tsay (Supervisor)

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