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Proceedings Paper

Channel model for watermarks subject to desynchronization attacks
Author(s): Robert Baeuml; Joachim J. Eggers; Roman Tzschoppe; Johannes Huber
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Paper Abstract

One of the most important practical problems of blind Digital Watermarking is the resistance against desynchronization attacks, one of which is the Stirmark random bending attack in the case of image watermarking. Recently, new blind digital watermarking schemes have been proposed which do not suffer from host-signal interference. One of these quantization based watermarking scheme is the Scalar Costa Scheme (SCS). We present an attack channel for SCS which tries to model typical artefacts of local desynchronization. Within the given channel model, the maximum achievable watermark rate for imperfectly synchronized watermark detection is computed. We show that imperfect synchronization leads to inter-sample-interference by other signal samples, independent from the considered watermark technology. We observe that the characteristics of the host signal play a major role in the performance of imperfectly synchronized watermark detection. Applying these results, we propose a resynchronization method based on a securely embedded pilot signal. The watermark receiver exploits the embedded pilot watermark signal to estimate the transformation of the sampling grid. This estimate is used to invert the desynchronization attack before applying standard SCS watermark detection. Experimental results for the achieved bit error rate of SCS watermark detection confirm the usefulness of the proposed resynchronization algorithm.

Paper Details

Date Published: 29 April 2002
PDF: 12 pages
Proc. SPIE 4675, Security and Watermarking of Multimedia Contents IV, (29 April 2002); doi: 10.1117/12.465286
Show Author Affiliations
Robert Baeuml, Friedrich-Alexander-Univ. Erlangen-Nuernberg (Germany)
Joachim J. Eggers, Friedrich-Alexander-Univ. Erlangen-Nuernberg (Germany)
Roman Tzschoppe, Friedrich-Alexander Univ. Erlangen-Nuremberg (Germany)
Johannes Huber, Friedrich-Alexander-Univ. Erlangen-Nuernberg (Germany)

Published in SPIE Proceedings Vol. 4675:
Security and Watermarking of Multimedia Contents IV
Edward J. Delp; Ping Wah Wong, Editor(s)

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