A New Measure of Watermarking Security: The Effective Key Length

Abstract

Whereas the embedding distortion, the payload and the robustness of digital watermarking schemes are well understood, the notion of security is still not completely well defined. The approach proposed in the last five years is too theoretical and solely considers the embedding process, which is half of the watermarking scheme. This paper proposes a new measure of watermarking security, called the effective key length, which captures the difficulty for the adversary to get access to the watermarking channel. This new methodology is applied here to additive spread spectrum schemes where theoretical and practical computations of the effective key length are proposed. Experimental protocols using either Monte-Carlo simulations, region approximation or rare event probability estimator allow good evaluation of this quantity. For Improved Spread Spectrum (ISS), our analysis exhibits setups where i) the robustness and the security of the scheme are superior to Spread Spectrum and ii) estimating the secret keys from the observations only is not the best way to break the scheme. Moreover a comparison with Correlation Aware Spread Spectrum (CASS) shows that ISS offers a better security than CASS for a given robustness.

Simple Countermeasure to Non-Linear Collusion Attacks Targeted for Spread-Spectrum Fingerprinting Scheme

“…The flowchart of embedding procedure is depicted in Fig. 3, where the feature extraction means the selection of frequency components [14], [15]. The feature extraction essentially depends on the targeted digital content.…”

Security analysis of radial-based 3D watermarking systems

“…In watermarking, the security against brute-force attacks depends both on the number of to-be-tested parametersε, and on the probability for the adversary to pick an equivalent parameter, which allows for a reliable decoding of a content that is watermarked with ϵ [7], [4]. In the QP framework, this probability is not easily tractable as ϵ controls multiple aspects of the watermark carrier computation.…”

“…For instance, it is common practice to rely on a 128-bit long secret key to derive pseudo-random parameters used in the watermarking algorithm and to invoke a cryptographic argument to argue that brute-force search would be computationally prohibitive [2], [3]. However, recent works have clearly showcased that distinct keys could yield equivalent parameters that grants watermarking decoding capabilities [4]. In other words, watermarking security should not be reduced to the length of the secret key.…”

Reversible Data Hiding Using Controlled Contrast Enhancement and Integer Wavelet Transform

“…D ATA hiding is applied extensively to the fields of ownership protection, fingerprinting, authentication and secret communication [1], [2]. The most classical data hiding leads to permanent distortions.…”