Watermark Embedding and Extraction Scheme Design by Two-stage Optimization for Illegal Replication Detection of Two-dimensional Barcodes

Abstract

Recently, two-dimensional (2D) barcodes displayed on mobile phones are becoming used for authentification such as airplane boarding pass and online payment. Digital watermarking is promising technology to detect illegal replication or fabrication of such 2D codes. However, due to geometric distortions and/or interferences between patterns of camera sensors and screen pixels, watermark may not be sufficiently extracted from subbands which are used when embedding the watermark. This paper proposes a two-stage optimization method for watermark embedding and extracting scheme design. The proposed method discriminates frequency subbands between for embedding and extraction, whereas general watermarking schemes extract the watermark from the same subbands as while embedding. To evaluate actual image deterioration by digital-analogue conversion with mobile phone screen and camera, the proposed method uses actual mobile phones to obtain real images of valid and replicated 2D codes. Experimental result have shown that the proposed two-stage optimization of watermark embedding and extracting schemes improved watermark performance for 2D code replication detection.