Towards geometrically robust data-hiding with structured codebooks

In this paper we analyze performance of practical robust data-hiding in channels with geometrical transformations. By applying information-theoretic argument we show that performance of a system designed based on both random coding and random binning principles is bounded by the same maximal achievable rate for the cases when communication channel includes geometrical transformations or not. Targeting to provide theoretic performance limits of practical robust data-hiding we model it using a multiple access channel (MAC) with side information (SI) available at one of encoders and present the bounds on achievable rates of reliable communications to such a protocol. Finally, considering template-based and redundant-based design of geometrically robust data-hiding systems, we perform security analysis of their performance and present results in terms of number of trial efforts the attacker needs to completely remove hidden informatio

Kernel Density Estimation Techniques for Monte Carlo Reactor Analysis.

Kernel density estimators (KDEs) are developed to estimate neutron scalar flux and reaction rate densities in Monte Carlo neutron transport simulations of pressurized water reactor benchmark problems in continuous energy. Previous work introduced the collision and track-length KDE for estimating scalar flux in radiation transport problems as an alternative to traditional histogram tallies. However, these estimators were not developed to estimate reaction rates and they were they not tested in continuous energy reactor physics problems. This dissertation expands upon previous work by developing KDEs that are capable of accurately estimating reaction rates in reactor physics problems. The current state of the art in KDEs is applied to estimate reaction rates in reactor physics problems, with significant bias observed at material interfaces. The Mean Free Path (MFP) KDE is introduced in order to reduce this bias, with results showing no significant bias in 1-D problems. The multivariate MFP KDE is derived and applied to 2-D benchmark problems. Results show that the multivariate MFP KDE produces results with significant variance resulting from particle events at resonance energies. The fractional MFP KDE is developed to reduce this variance. An approximation to the MFP KDE is introduced to improve computational performance of the algorithm at the cost of introducing additional bias into the estimates. A volume-average KDE is derived in order to directly compare KDE and histogram results and is used to determine the bias introduced by the approximation to the MFP KDE. A KDE is derived for cylindrical coordinates, and the cylindrical MFP KDE is derived to capture distributions in reactor pincell problems. The cylindrical MFP KDE is applied to estimate distributions on an IFBA pincell, a quarter assembly of pincells, a depleted pincell, and on an unstructured mesh representation of a pincell. The results indicate that the cylindrical MFP KDE and fractional MFP KDE are capable of accurately capturing reaction rates in reactor physics benchmark problems. This dissertation also describes the acceleration of the KDE via heterogeneous computing with GPUs. The algorithm development is described along with optimization strategies on the GPU. Speedups of 1.4-5 are observed for several benchmark problems.PHDNuclear Engineering & Radiological SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/135841/1/tpburke_1.pd

Achievable Rate Analysis of Geometrically Robust Data-Hiding Codes In Asymptotic Set-ups

Geometrical transformations bring synchronization problems into the robust digital data-hiding. Previous works on this subject were concentrated on the robustness to particular geometrical transformations. In this paper, the achievable rates of reliable robust data-hiding in channels with geometrical transformations are investigated from an informationtheoretic point of view for theoretical set-ups, where lengths of data sequences asymptotically approach infinit

ACHIEVABLE RATE ANALYSIS OF GEOMETRICALLY ROBUST DATA-HIDING CODES IN ASYMPTOTIC SET-UPS

Geometrical transformations bring synchronization problems into the robust digital data-hiding. Previous works on this subject were concentrated on the robustness to particular geometrical transformations. In this paper, the achievable rates of reliable robust data-hiding in channels with geometrical transformations are investigated from an informationtheoretic point of view for theoretical set-ups, where lengths of data sequences asymptotically approach infinity. 1

Contribution des filtres LPTV et des techniques d'interpolation au tatouage numérique

Les Changements d'Horloge Périodiques (PCC) et les filtres Linéaires Variant Périodiquement dans le Temps (LPTV) sont utilisés dans le domaine des télécommunications multi-utilisateurs. Dans cette thèse, nous montrons que, dans l'ensemble des techniques de tatouage par étalement de spectre, ils peuvent se substituer à la modulation par code pseudo-aléatoire. Les modules de décodage optimal, de resynchronisation, de pré-annulation des interférences et de quantification de la transformée d'étalement s'appliquent également aux PCC et aux filtres LPTV. Pour le modèle de signaux stationnaires blancs gaussiens, ces techniques présentent des performances identiques à l'étalement à Séquence Directe (DS) classique. Cependant, nous montrons que, dans le cas d'un signal corrélé localement, la luminance d'une image naturelle notamment, la périodicité des PCC et des filtres LPTV associée à un parcours d'image de type Peano-Hilbert conduit à de meilleures performances. Les filtres LPTV sont en outre un outil plus puissant qu'une simple modulation DS. Nous les utilisons pour effectuer un masquage spectral simultanément à l'étalement, ainsi qu'un rejet des interférences de l'image dans le domaine spectral. Cette dernière technique possède de très bonnes performances au décodage. Le second axe de cette thèse est l'étude des liens entre interpolation et tatouage numérique. Nous soulignons d'abord le rôle de l'interpolation dans les attaques sur la robustesse du tatouage. Nous construisons ensuite des techniques de tatouage bénéficiant des propriétés perceptuelles de l'interpolation. La première consiste en des masques perceptuels utilisant le bruit d'interpolation. Dans la seconde, un schéma de tatouage informé est construit autour de l'interpolation. Cet algorithme, qu'on peut relier aux techniques de catégorisation aléatoire, utilise des règles d'insertion et de décodage originales, incluant un masquage perceptuel intrinsèque. Outre ces bonnes propriétés perceptuelles, il présente un rejet des interférences de l'hôte et une robustesse à diverses attaques telles que les transformations valumétriques. Son niveau de sécurité est évalué à l'aide d'algorithmes d'attaque pratiques. ABSTRACT : Periodic Clock Changes (PCC) and Linear Periodically Time Varying (LPTV) filters have previously been applied to multi-user telecommunications in the Signal and Communications group of IRIT laboratory. In this thesis, we show that in each digital watermarking scheme involving spread-spectrum, they can be substituted to modulation by a pseudo-noise. The additional steps of optimal decoding, resynchronization, pre-cancellation of interference and quantization of a spread transform apply also to PCCs and LPTV filters. For white Gaussian stationary signals, these techniques offer similar performance as classical Direct Sequence (DS) spreading. However we show that, in the case of locally correlated signals such as image luminance, the periodicity of PCCs and LPTV filters associated to a Peano-Hilbert scan leads to better performance. Moreover, LPTV filters are a more powerful tool than simple DS modulation. We use LPTV filters to conduct spectrum masking simultaneous to spreading, as well as image interference cancellation in the spectral domain. The latter technique offers good decoding performance. The second axis of this thesis is the study of the links between interpolation and digital watermarking.We stress the role of interpolation in attacks on the watermark.We propose then watermarking techniques that benefit from interpolation perceptual properties. The first technique consists in constructing perceptualmasks proportional to an interpolation error. In the second technique, an informed watermarking scheme derives form interpolation. This scheme exhibits good perceptual properties, host-interference rejection and robustness to various attacks such as valumetric transforms. Its security level is assessed by ad hoc practical attack algorithms