Watermarking security: theory and practice

This article proposes a theory of watermarking security based on a cryptanalysis point of view. The main idea is that information about the secret key leaks from the observations, for instance watermarked pieces of content, available to the opponent. Tools from information theory (Shannon's mutual information and Fisher's information matrix) can measure this leakage of information. The security level is then defined as the number of observations the attacker needs to successfully estimate the secret key. This theory is applied to two common watermarking methods: the substitutive scheme and the spread spectrum based techniques. Their security levels are calculated against three kinds of attack. The experimental work illustrates how Blind Source Separation (especially Independent Component Analysis) algorithms help the opponent exploiting this information leakage to disclose the secret carriers in the spread spectrum case. Simulations assess the security levels derived in the theoretical part of the article

Watermarking security part II: practice

This second part focuses on estimation of secret parameters of some practical watermarking techniques. The first part reveals some theoretical bounds of information leakage about secret keys from observations. However, as usual in information theory, nothing has been said about practical algorithms which pirates use in real life application. Whereas Part One deals with the necessary number of observations to disclose secret keys (see definitions of security levels), this part focuses on the complexity or the computing power of practical estimators. Again, we are inspired here by the work of Shannon as in his famous article [15], he has already made a clear cut between the unicity distance and the work of opponents' algorithm. Our experimental work also illustrates how Blind Source Separation (especially Independent Component Analysis) algorithms help the opponent exploiting this information leakage to disclose the secret carriers in the spread spectrum case. Simulations assess the security levels theoretically derived in Part One

Watermarking security part I: theory

This article proposes a theory of watermarking security based on a cryptanalysis point of view. The main idea is that information about the secret key leaks from the observations, for instance watermarked pieces of content, available to the opponent. Tools from information theory (Shannon's mutual information and Fisher's information matrix) can measure this leakage of information. The security level is then defined as the number of observations the attacker needs to successfully estimate the secret key. This theory is applied to common watermarking methods: the substitutive scheme and spread spectrum based techniques. Their security levels are calculated against three kinds of attack

TSAR: Secure Transfer OF High Resolution Art Images

International audienceThe EROS (European Research Open System) database hosted at the Centre de Recherche et de Restauration des Musées de France (C2RMF) is one of the largest database in the world of Cultural Heritage that is widely recognized for its high resolution images. The French research project TSAR (Transfert Sécurisé d'images d'Art haute Resolution) aims to give the possibility to open this huge amount of art images in a secure and efficient way. For this purpose, we use a mixture of techniques to assure the security of the data involving cryptography and watermarking techniques as well as multi-resolution compression scheme together with a region-level representation. These algorithms are especially optimized for high resolution art images. In particular, this means that the quality of the transmitted images have to be not reduced, implying the use of lossless coding techniques. In this paper we present an overall scheme that provides an efficient, consistent solution for secure data browsing, viewing and transmitting, adoptable by any Cultural Heritage institution

Security and robustness constraints for spread-spectrum Tardos fingerprinting

International audienceThis paper presents a practical analysis of the impact of robustness and security on Tardos' collusion-secure fingerprinting codes using spread-spectrum watermarking modulations. In this framework, we assume that the coalition has to face an embedding scheme of given security level and consequently has to suffer a probability of wrongly estimating their embedded symbols. We recall the Worst Case Attack associated to this probability, e.g. the optimal attack which minimises the mutual information between the sequence of a colluder and the pirated one. For a given achievable rate of the Tardos' fingerprinting model, we compare the Improved Spread-Spectrum embedding versus a new secure embedding (called rho-Circular Watermarking) considering the AWGN channel. We show that secure embeddings are more immune to decoding errors than non-secure ones while keeping the same fingerprinting capacity

Frequent EGFR Positivity and Overexpression in High-Grade Areas of Human MPNSTs

Malignant peripheral nerve sheath tumours (MPNSTs) are highly malignant and resistant. Transformation might implicate up regulation of epidermal growth factor receptor (EGFR). Fifty-two MPNST samples were studied for EGFR, Ki-67, p53, and survivin expression by immunohistochemistry and for EGFR amplification by in situ hybridization. Results were correlated with clinical data. EGFR RNA was also quantified by RT-PCR in 20 other MPNSTs and 14 dermal neurofibromas. Half of the patients had a neurofibromatosis type 1 (NF1). EGFR expression, detected in 86% of MPNSTs, was more frequent in NF1 specimens and closely associated with high-grade and p53-positive areas. MPNSTs expressed more EGFR transcripts than neurofibromas. No amplification of EGFR locus was observed. NF1 status was the only prognostic factor in multivariate analysis, with median survivals of 18 and 43 months for patients with or without NF1. Finally, EGFR might become a new target for MPNSTs treatment, especially in NF1-associated MPNSTs

Cryptographie, stéganographie et tatouage : des secrets partagés

National audienceLa cryptographie est reconnue comme l’« art » des codes secrets. Moins connus, la stéganographie et le tatouage constituent deux autres « principes de camouflage »

Contributions au tatouage des maillages surfaciques 3D

Les méthodes de tatouage actuelles pour les maillages surfaciques 3Dsont essentiellement le fait de la communauté CAO, et sont assez peuadaptées à une étude en termes de tatouage. Dans un premier temps, nousavons abordé dans ce travail le tatouage par invariants géométriques,dédié aux applications de tatouage fragile. Dans un deuxième temps, nousavons utilisé l'espace de la décomposition spectrale de la géométrieafin d'y enfouir une marque que nous voulons robuste face à laquantification des coefficients spectraux. En tatouage fragile, nous proposons notamment une approche flexible etmodulaire permettant l'analyse fine, d'un point de vue du tatouage, desperformances de notre méthode (classe de robustesse, probabilité defausse alarme, etc.) Les applications visées par cette approcheconcernent tant la stéganographie que l'intégrité ou l'authentificationdes maillages. Nous décrivons une méthode de tatouage fragile pourl'authentification construite avec les modules que nous présentons. Le tatouage dans l'espace de la décomposition spectrale de la géométrie,à travers son étude face à la compression, implique le développementd'un codeur de source géométrique spectral. Nous étudions lesdifficultés liées à l'implantation d'une telle décomposition, tant pourle codage de source que pour le tatouage. Nous terminons en montrant quenotre schéma de tatouage se révèle robuste face à la compressiongéométrique spectrale

Contributions to watermarking of 3D meshes/Contributions au tatouage des maillages surfaciques 3D

We present two watermarking schemes for 3D meshes : - watermarking with geometrical invariant for fragile watermarking towards authentication and integrity purposes - watermarking in the geometrical spectral domain towards robust watermarking / Nous présentons deux schémas de tatouage pour maillages surfaciques 3D : - tatouage fragile par invariants géométriques pour l'authentification et l'intégrité - tatouage robuste dans l'espace de la décomposition spectrale(FSA 3)--UCL, 200

Cryptographie, stéganographie et tatouage : des secrets partagés

National audienceLa cryptographie est reconnue comme l’« art » des codes secrets. Moins connus, la stéganographie et le tatouage constituent deux autres « principes de camouflage »