COUNTER-TAMPERING OF RASTER CHART DATA BASED ON DIGITAL WATERMARK
F. Cheng, Z. Tian, J. Guo, G.X. Chen
Dalian Naval Academy, Department of Hydrographic Surveying and Charting, Dalian, China
With the persistent development of digital charts and their applications, the integrality validation of chart data and their sources, e.g. RS images and surveyed data by echo-sounding, is getting more and more important. The problem of whether the data are from reliable sources, and whether the data were undergone unauthorized modification, will become a key in the chart production and use. Unfortunately, the effort to solve this problem was focused on the enforcement of regulations and administration, no effective technical means was set up or even discussed yet.
Fragile watermark is very sensitive to the data changes of its carrier. It is invisible, fragile, will not disturb the functioning of chart data, and is widely used in authentication, counter-tampering, safety and integrity of data.
Based on the essential requirement of data security, the paper researched on the chart data validation by fragile watermark techniques for raster-oriented chart data. After analysis of the basic demand of chart data security and of tamper-positioning, this paper put forward an arithmetic of improved self-embedded fragile watermarking for raster data. Parameters were selected to adjust the sensitivity of counter-tampering. The arithmetic was fragile to various tampering, and had the advantage of more precise tamper-positioning to the existing methods of image authentication. A protocol was developed to realize precise tamper-positioning, with the help of Chaos Theory, Wavelet Theory and Human Visibility System (HVS). Simulation experiment proved that the watermarks embedded are good at invisibility, and chart quality depressed less. It is very suitable for chart data protection.