Most of the watermarking algorithms can still be defeated by geometric distortions today. If the weakness against global distortions can almost be considered as solved, local geometric distortions such as the ones introduced by StirMark remain a major issue. An original resynchronization method is consequently proposed in this report as a potential countermeasure against such attacks. The basic idea consists in interlacing resynchronization bits with the bits carrying the payload during the watermark embedding. During the extraction, those bits are used as anchor points to estimate and compensate for small local and global geometric distortions. This registration procedure is performed using an Elastic Graph Matching (EGM) approach.
Watermark resynchronization based on elastic graph matching for enhanced robustness against local geometric distortions
Research report RR-04-113
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