Press Releases

Abstracts from the Top Three Best Papers as Awarded by the Digital Watermarking Alliance

The Digital Watermarking Alliance granted awards to three teams of researchers for their papers that demonstrate originality, creativity, clarity and potential impact on the field of watermarking.

Abstracts from the winning entries are listed below.
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First Place Paper

The Square Root Law of Steganographic Capacity for Markov Covers
Tomas Fillera, Andrew D. Kerb and Jessica Fridricha
Department of Electrical and Computer Engineering – SUNY Binghamton
Oxford University Computing Laboratory

Abstract
It is a well-established result that steganographic capacity of perfectly secure stegosystems grows linearly with the number of cover elements-secure steganography has a positive rate. In practice, however, neither the Warden nor the Steganographer has perfect knowledge of the cover source and thus it is unlikely that perfectly secure stegosystems for complex covers, such as digital media, will ever be constructed. This justifies study of secure capacity of imperfect stegosystems. Recent theoretical results from batch steganography, supported by experiments with blind steganalyzers, point to an emerging paradigm: whether steganography is performed in a large batch of cover objects or a single large object, there is a wide range of practical situations in which secure capacity rate is vanishing. In particular, the absolute size of secure payload appears to only grow with the square root of the cover size. In this paper, we study the square root law of steganographic capacity and give a formal proof of this law for imperfect stegosystems, assuming that the cover source is a stationary Markov chain and the embedding changes are mutually independent.

Second Place Paper

Joint Detection-Estimation Games for Sensitivity Analysis Attacks
Maha El Choubassia and Pierre Moulinb
University of Illinois, Beckman Institute and ECE Department

Abstract
Sensitivity analysis attacks aim at estimating a watermark from multiple observations of the detector's output. Subsequently, the attacker removes the estimated watermark from the watermarked signal. In order to measure the vulnerability of a detector against such attacks, we evaluate the fundamental performance limits for the attacker's estimation problem. The inverse of the Fisher information matrix provides a bound on the covariance matrix of the estimation error. A general strategy for the attacker is to select the distribution of auxiliary test signals that minimizes the trace of the inverse Fisher information matrix. The watermark detector must trade off two conflicting requirements: (1) reliability, and (2) security against sensitivity attacks. We explore this tradeoff and design the detection function that maximizes the trace of the attacker's inverse Fisher information matrix while simultaneously guaranteeing a bound on the error probability. Game theory is the natural framework to study this problem, and considerable insights emerge from this analysis.

Third Place Paper

Exhibition QIM-based Watermarking for Digital Cinema
Pilar Callau, Rony Darazi and Benoît Macq
Communications and Remote Sensing Laboratory Université Catholique de Louvain, Belgium

Abstract
The copyright protection of Digital Cinema requires the insertion of forensic watermarks during exhibition playback. This paper presents a low-complexity exhibition watermarking method based on quantization index modulation (QIM) and embedded in the DCI compliant decoder. Watermark embedding is proposed to fit in the JPEG2000 decoding process, prior to the inverse wavelet transform and such as it has a minimal impact on the image quality, guarantying a strong link between decompression and watermarking. The watermark is embedded by using an adaptive-Spread Transform Dither Modulation (STDM) method, based on a new multi-resolution perceptual masking to adapt watermark strength. Watermark detection is thereafter performed over the wavelet transformation of the recovered images. The proposed approach offers a wide range of channel capacities according to robustness to several kinds of distortions while maintaining a low computational complexity. Watermarking detection performance on Digital Cinema pictures captured with a video camera from a viewing room has been preliminary assessed, showing very promising results. The proposed approach provides high levels of imperceptibility, yet good robustness to degradations resulting from camcorder exhibition capture, to common signal processing operations such as filtering or re-sampling, and to very high compression.