Página 1 dos resultados de 61 itens digitais encontrados em 0.000 segundos

Reintegração social: um diálogo entre a sociedade e o cárcere; Social reintegration: a dialogue between the society and the prison

Peter Filho, Jovacy
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 16/08/2011 PT
Relevância na Pesquisa
16.68%
A presente pesquisa consistiu em identificar, a partir de um enfoque crítico e clínicocriminológico, o que caracteriza e singulariza a Reintegração Social frente às demais propostas político-criminais tradicionalmente aplicadas ao cenário da execução penal. A partir deste objetivo, foram sendo desdobradas as filigranas das clássicas estratégias político-criminais (tratamento penitenciário e ressocialização) a fim de investigar a proximidade os limites teóricos entre elas e a Reintegração Social, além de se debruçar na idéia que propõe uma filosofia dialogal como mecanismo de aproximação e identificação plurais entre a sociedade e o cárcere.; The present research was to identify, from a critical, clinical and criminological, which characterizes the Social Reintegration against other proposals for criminal policy traditionally applied to the landscape of criminal enforcement. From this goal, the watermarks have been deployed on classical criminal policy (prison treatment and social rehabilitation) to investigate the theoretical limits of the closeness between them and Social Reintegration, and to address the idea that proposes a dialogical philosophy as a mechanism approach and identification of plural society and prison.

Marcas de água: Arquivo Histórico Parlamentar (monarquia constitucional 1821-1910)

Carreira, Maria de São Luiz da Silva
Fonte: Universidade de Lisboa Publicador: Universidade de Lisboa
Tipo: Dissertação de Mestrado
Publicado em //2012 POR
Relevância na Pesquisa
17.85%
Tese de mestrado, Ciências da Documentação e Informação (Arquivística), Universidade de Lisboa, Faculdade de Letras, 2013; Este trabalho estabelece um inventário das filigranas e contramarcas encontradas nas actas manuscritas de 1821 a 1910 – período relativo à Monarquia Constitucional - , do Arquivo Histórico Parlamentar e apresenta a história dessas marcas, sendo precedido de um estudo das mesmas. As marcas constantes do inventário são de origem holandesa, inglesa, francesa e portuguesa. O estudo refere, ainda que brevemente, métodos de reprodução das marcas de água do papel e estabelecemos a relação entre os países produtores de papel de elevada qualidade durante o século XIX e o seu consumo, nomeadamente do que se refere às actas manuscritas. Foram registadas também as variantes das filigranas consideradas mais significativas, além do predomínio de motivos temáticos nas marcas inventariadas.; ABSTRACT: This project establishes an inventory of paper watermarks and countermarks found from 1821 to 1910 – during the Constitutional Monarchy period – found in the Parliamentary History Archive, presenting a history of those marks. The paper watermarks found are from Dutch, English, French and Portuguese origin. This study mentions...

GenInfoGuard—A Robust and Distortion-Free Watermarking Technique for Genetic Data

Iftikhar, Saman; Khan, Sharifullah; Anwar, Zahid; Kamran, Muhammad
Fonte: Public Library of Science Publicador: Public Library of Science
Tipo: Artigo de Revista Científica
Publicado em 17/02/2015 EN
Relevância na Pesquisa
17.31%
Genetic data, in digital format, is used in different biological phenomena such as DNA translation, mRNA transcription and protein synthesis. The accuracy of these biological phenomena depend on genetic codes and all subsequent processes. To computerize the biological procedures, different domain experts are provided with the authorized access of the genetic codes; as a consequence, the ownership protection of such data is inevitable. For this purpose, watermarks serve as the proof of ownership of data. While protecting data, embedded hidden messages (watermarks) influence the genetic data; therefore, the accurate execution of the relevant processes and the overall result becomes questionable. Most of the DNA based watermarking techniques modify the genetic data and are therefore vulnerable to information loss. Distortion-free techniques make sure that no modifications occur during watermarking; however, they are fragile to malicious attacks and therefore cannot be used for ownership protection (particularly, in presence of a threat model). Therefore, there is a need for a technique that must be robust and should also prevent unwanted modifications. In this spirit, a watermarking technique with aforementioned characteristics has been proposed in this paper. The proposed technique makes sure that: (i) the ownership rights are protected by means of a robust watermark; and (ii) the integrity of genetic data is preserved. The proposed technique—GenInfoGuard—ensures its robustness through the “watermark encoding” in permuted values...

Clustered-dot periodic halftones : modeling, modulation, and applications

Oztan, Basak (1980 - ); Sharma, Gaurav
Fonte: University of Rochester Publicador: University of Rochester
Tipo: Tese de Doutorado Formato: Number of Pages:xx, 203 leaves
ENG
Relevância na Pesquisa
17.64%
Thesis (Ph. D.)--University of Rochester. Dept. of Electrical and Computer Engineering, 2010.; This thesis addresses analyses and applications of periodic clustered-dot halftones that are widely utilized in electrophotographic (laser) and lithographic (offset) printing. Within this broad setting, we address three specific problems: 1) the modeling and analysis of the color shifts induced by inter-separation misregistration, 2) phase and frequency modulation in clustered-dot halftones for watermark embedding and content adaptive halftoning, and 3) per-separation color halftone watermarking by exploiting differences in spatial periodicity and colorant spectra of the individual colorant halftones. The work and contributions in each of these areas are summarized in the following. Misregistration-induced color shifts for periodic clustered-dot color halftones are characterized by combining the Neugebauer model with a periodic lattice representation for the individual halftones to obtain a spatio-spectral model for the color print. Conditions for color misregistration invariance are identified by using the model in terms of colorant spectra, periodicity of the individual separation halftones, dot shapes, and misregistration displacements. Furthermore...

Embedded watermarking for image verification in telemedicine

Osborne, Dominic
Fonte: Universidade de Adelaide Publicador: Universidade de Adelaide
Tipo: Tese de Doutorado Formato: 1346482 bytes; 87441 bytes; application/pdf; application/pdf
Publicado em //2005 EN
Relevância na Pesquisa
17.31%
Wireless communication technology has provided increased opportunity for applications such as telemedicine. This work focuses on the end application of teleradiology, targeting the communication of digital diagnostic images to remote locations for diagnosis and treatment. Medical images have conventionally been of large size and stored without loss of redundancy. Recent research has demonstrated that acceptable levels of Joint Picture Experts Group ( JPEG ) compression may be used on these image types without loss of diagnostic content. This has provided an opportunity for more rapid image transmission in wireless environments. One of the most pressing challenges that remain are techniques to verify the integrity of crucial diagnostic feature information that may be compromised with excessive use of standard compression methods. An authentication watermarking technique is presented, which extracts critical feature information from the Region of Interest ( ROI ) and embeds a series of robust watermarks into the Region of Backgrounds ( ROB ) surrounding this location. This thesis will consider only the effects of distortions due to compression standards and presents a body of work that is a step towards a future study for considering compression together with channel noise introduced by the wireless environment. The following key contributions have been made in this thesis : 1. A novel technique to provide crucial feature authentication without introducing embedding distortions into these regions by using multiple robust watermarks 2. Improved performance over earlier methods including superior robustness to DCT quantisation and complete JPEG image compression. Image fidelity is significantly improved with less distortion introduced. Smaller signatures can be used to authenticate essential image information than with conventional methods...

Aproximación codicológica al "Lanzarote del Lago" castellano : ms. 9611 de la Biblioteca Nacional de España

Belenguer, Iria
Fonte: Universidad de Alcalá. Servicio de Publicaciones Publicador: Universidad de Alcalá. Servicio de Publicaciones
Tipo: Artigo de Revista Científica Formato: application/pdf
SPA
Relevância na Pesquisa
27.31%
Se analiza la configuración formal del manuscrito BNM 9611 de la Biblioteca Nacional de España, tanto en sus aspectos externos (papel y marcas de agua, fasciculación, paleografia) como internos, atendiendo especialmente a su identificación en el proceso de transmisión textual de la versión Vulgata del ciclo narrativo artúrico Lancelot du Lac en la Península Ibérica.; The sixteenth-century Castilian version of the Vulgate Lancelot du Lac is examined through its formal disposition, regarding external features such as watermarks and quire organization; and more importantly, the internal attributes that allow to place this manuscript in the complex thread of transmission from the original French Arthurian narrative to the late Iberian versions.

Marcas d\'água de autenticação para imagens binárias: marcas reversíveis e marcas para o padrão JBIG2.; Authentication watermaking techniques for binary images: reversible watermarks and watermarks for JBIG2.

Pamboukian, Sergio Vicente Denser
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 01/06/2007 PT
Relevância na Pesquisa
17.31%
Esteganografia é uma técnica utilizada para ocultar uma informação secreta dentro de outro tipo de informação sem perda de qualidade da informação hospedeira e com o objetivo de extrair a informação posteriormente. Esteganografia reversível permite a exata restauração (sem perda) do sinal hospedeiro original após a extração da informação oculta. Várias ténicas reversíveis têm sido desenvolvidas, mas nenhuma delas parece ser apropriada para imagens binárias. Uma técnica de marca d\'água faz uso de técnicas esteganográficas para inserir informação em uma imagem hospedeira, com o intuito de fazer uma asserção sobre a imagem no futuro. Uma marca d\'água de autenticação (AWT) insere uma informação oculta na imagem com a intenção de detectar qualquer alteração acidental ou maliciosa na imagem. Uma AWT normalmente usa criptografia de chave secreta ou chave pública para computar a assinatura de autenticação da imagem, inserindo-a na própria imagem. JBIG2 é um padrão internacional para compressão de imagens binárias (com ou sem perda). Ele decompõe a imagem em várias regiões (texto, meio-tom e genérica) e codifica cada região usando o método mais apropriado. A criação de AWTs seguras para imagens binárias comprimidas é um importante problema prático. Porém...

Uma alternativa publica para o metodo de marcas d'agua Raster em mapas vetoriais (RAWVec); A blind alternative for raster watermerking vector maps (RAWVec)

Karina Mochetti de Magalhães
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 11/03/2009 PT
Relevância na Pesquisa
17.31%
Marcas d'água vem sendo utilizadas em vários tipos de arquivos de multimídia, como áudio, vídeo e imagens de bitmap, para combater sua copia e distribuição ilegais. Somente com a popularização dos Sistemas de Informação Geográfica (GIS) e da utilização de dados espaciais na Web, marcas d'água para mapas vetoriais ganharam maior atenção, principalmente porque este tipo de imagem possui produção cara, mas pode ser reproduzido facilmente. Esse trabalho revisa o método RAWVec, que insere uma marca d'água representada por uma imagem raster ou bitmap num mapa vetorial, e apresenta uma alternativa publica para tal método; Watermarks have been used for a long time in several digital media to avoid the illegal copy and distribution of these items. Only with the popularization of Geographic Information Systems (GIS) and the use of spatial data on the Web, watermarks for vector maps gained more attention, mostly because vector maps are expensive to produce, but easy to copy. This work reviews the RAWVec Method that embeds a watermark, in the form of a bitmap image, into digital vector maps; and presents a semi-blind alternative method

Marcas d'agua visuais em mapas vetoriais; Visual watermarks in vector maps

Douglas Aurelio Marques
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 18/08/2005 PT
Relevância na Pesquisa
27.31%
Com a proliferação dos sistemas de informação geográfica (GIS) e a disponibilidade crescente de dados espaciais, empresas de vários segmentos têm tido a oportunidade de criar bases de dados geográficas para uso próprio ou fornecimento de serviços. A representação de informações nessas bases de dados se dá através de mapas em formato vetorial, produzidos geralmente a um alto custo, mas de fácil reprodução. Este trabalho tem como objetivo a apresentação de um novo método para inserção de marcas d'água visuais em mapas vetoriais digitais, para combater a cópia e a distribuição ilegais desse tipo de mídia. Neste novo método, a marca d'água, formada pelos pixels de uma imagem, é inserida em um mapa através de deslocamentos controlados de suas coordenadas. A detecção da marca d'água em um mapa é feita com a extração da imagem inserida e sua comparação com a original. Vários experimentos práticos mostram que o método é bastante resistente a diversos tipos de ataque, como cropping, adição de coordenadas, alteração da ordem das entidades, inserção de ruído, transformações locais e globais e combinações desses ataques.; The proliferation of geographic information systems (GIS) and the increasing availability of spatial data makes it possible to create geographic databases for a large variety of ends and services. The information in these databases is represented by digital vector maps which are expensive to produce...

Marca d'água digital : autenticação de imagens digitais; Digital watermark authentication of digital images

Nunes, Sílton Leonardo Paiva
Fonte: Universidade Federal do Rio Grande do Sul Publicador: Universidade Federal do Rio Grande do Sul
Tipo: Trabalho de Conclusão de Curso Formato: application/pdf
POR
Relevância na Pesquisa
17.64%
A disseminação de imagens digitais pela internet criou novos desafios relacionados à autoria e integridade dos documentos transacionados. Um documento de texto submetido à criptografia ou certificação digital fica protegido contra qualquer alteração, por menor que ela seja. Ao contrário, uma imagem deve ser considerada autêntica mesmo que o seu código tenha sofrido alguns tipos de alterações, desde que não mudem a essência da informação contida na imagem, como compressão (JPEG por exemplo), ajuste de brilho, de contraste, entre outros tratamentos usuais. Neste contexto, uma das soluções para proteção de autoria e integridade de imagens digitais é o uso de marcas d'água digitais, as quais são conceitualmente semelhantes às marcas d'água usadas em documentos físicos, como o papel-moeda. Este trabalho tem por objetivo fornecer ao leitor um guia simples sobre marcas d'água digitais, incluindo características e aplicabilidade de marcas d'água imperceptíveis em imagens digitais. Ao final, uma bateria de testes avalia a robustez de marcas d'água inseridas por um software líder de mercado (Photoshop e Digimarc) contra ataques maliciosos e tratamentos usuais.; The spread of digital images throughout the Internet has created new challenges in regards to authorship and integrity of the exchanged documents. A text document submitted to criptography or digital certification is protected against any alteration...

Multi-marcação de vídeo baseada em marca d'água LWT-SVD usando abordagem lateral

Fung, Charles Way Hun
Fonte: Curitiba Publicador: Curitiba
Tipo: Dissertação de Mestrado
POR
Relevância na Pesquisa
27.85%
Digital videos have become the most used way to communicate, however these data are easily copied and distributed. That happen due the growing number of tools that are create with this goal, causing breach of copyright and illegal distribution of content. The most studied solution that can solve this problem are the digital watermarks that provide security like authentication and tamper detection. In this work, we developed a new method of embedding and extracting watermarks in a video using a process called side view. This process allows watermark a block of frames. The several watermarks embedded can be used like redundance to grow the robustness of the method against attacks. The tests followed the standard benchmarks Vidmark and Stirmark that show the performance of the method in keep the watermark even after attacks.; CAPES; Vídeos digitais se tornaram uma forma de comunicação altamente utilizada na rede, entretanto estes dados são facilmente copiados e distribuídos. Isto se deve ao crescente número de ferramentas que surgiram com este objetivo, causando quebra dos direitos autorais e distribuição ilegal de conteúdo. A solução mais estudada para este problema são as marcas d'água digitais, que provêm segurança em forma de autenticação e verificação de violação. Neste trabalho...

Perceptual Copyright Protection Using Multiresolution Wavelet-Based Watermarking And Fuzzy Logic

Hsieh, Ming-Shing
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 29/07/2010
Relevância na Pesquisa
17.99%
In this paper, an efficiently DWT-based watermarking technique is proposed to embed signatures in images to attest the owner identification and discourage the unauthorized copying. This paper deals with a fuzzy inference filter to choose the larger entropy of coefficients to embed watermarks. Unlike most previous watermarking frameworks which embedded watermarks in the larger coefficients of inner coarser subbands, the proposed technique is based on utilizing a context model and fuzzy inference filter by embedding watermarks in the larger-entropy coefficients of coarser DWT subbands. The proposed approaches allow us to embed adaptive casting degree of watermarks for transparency and robustness to the general image-processing attacks such as smoothing, sharpening, and JPEG compression. The approach has no need the original host image to extract watermarks. Our schemes have been shown to provide very good results in both image transparency and robustness.; Comment: 13 pages, 7 figures

Watermarking Digital Images Based on a Content Based Image Retrieval Technique

Tsolis, Dimitrios K.; Sioutas, Spyros; Papatheodorou, Theodore S.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 17/10/2008
Relevância na Pesquisa
17.64%
The current work is focusing on the implementation of a robust watermarking algorithm for digital images, which is based on an innovative spread spectrum analysis algorithm for watermark embedding and on a content-based image retrieval technique for watermark detection. The highly robust watermark algorithms are applying "detectable watermarks" for which a detection mechanism checks if the watermark exists or no (a Boolean decision) based on a watermarking key. The problem is that the detection of a watermark in a digital image library containing thousands of images means that the watermark detection algorithm is necessary to apply all the keys to the digital images. This application is non-efficient for very large image databases. On the other hand "readable" watermarks may prove weaker but easier to detect as only the detection mechanism is required. The proposed watermarking algorithm combine's the advantages of both "detectable" and "readable" watermarks. The result is a fast and robust watermarking algorithm.; Comment: 18 pages, 4 figures, 4 tables, submitted to Multimedia Tools and Applications Journal, Springer

Invisible Flow Watermarks for Channels with Dependent Substitution, Deletion, and Bursty Insertion Errors

Gong, Xun; Rodrigues, Mavis; Kiyavash, Negar
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
27.64%
Flow watermarks efficiently link packet flows in a network in order to thwart various attacks such as stepping stones. We study the problem of designing good flow watermarks. Earlier flow watermarking schemes mostly considered substitution errors, neglecting the effects of packet insertions and deletions that commonly happen within a network. More recent schemes consider packet deletions but often at the expense of the watermark visibility. We present an invisible flow watermarking scheme capable of enduring a large number of packet losses and insertions. To maintain invisibility, our scheme uses quantization index modulation (QIM) to embed the watermark into inter-packet delays, as opposed to time intervals including many packets. As the watermark is injected within individual packets, packet losses and insertions may lead to watermark desynchronization and substitution errors. To address this issue, we add a layer of error-correction coding to our scheme. Experimental results on both synthetic and real network traces demonstrate that our scheme is robust to network jitter, packet drops and splits, while remaining invisible to an attacker.

WaterRPG: A Graph-based Dynamic Watermarking Model for Software Protection

Chionis, Ioannis; Chroni, Maria; Nikolopoulos, Stavros D.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 17/03/2014
Relevância na Pesquisa
17.31%
Software watermarking involves embedding a unique identifier or, equivalently, a watermark value within a software to prove owner's authenticity and thus to prevent or discourage copyright infringement. Towards the embedding process, several graph theoretic watermarking algorithmic techniques encode the watermark values as graph structures and embed them in application programs. Recently, we presented an efficient codec system for encoding a watermark number $w$ as a reducible permutation graph $F[\pi^*]$ through the use of self-inverting permutations $\pi^*$. In this paper, we propose a dynamic watermarking model, which we call WaterRPG, for embedding the watermark graph $F[\pi^*]$ into an application program $P$. The main idea behind the proposed watermarking model is a systematic use of appropriate calls of specific functions of the program $P$. More precisely, for a specific input $I_{key}$ of the program $P$, our model takes the dynamic call-graph $G(P, I_{key})$ of $P$ and the watermark graph $F[\pi^*]$, and produces the watermarked program $P^*$ having the following key property: its dynamic call-graph $G(P^*, I_{key})$ is isomorphic to the watermark graph $F[\pi^*]$. Within this idea the program $P^*$ is produced by only altering appropriate calls of specific functions of the input application program $P$. We have implemented our watermarking model WaterRPG in real application programs and evaluated its functionality under various and broadly used watermarking assessment criteria. The evaluation results show that our model efficiently watermarks Java application programs with respect to several watermarking metrics like data-rate...

Evaluating Effectiveness of Tamper Proofing on Dynamic Graph Software Watermarks

Khiyal, Malik Sikandar Hayat; Khan, Aihab; Amjad, Sehrish; Khalil, M. Shahid
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 12/01/2010
Relevância na Pesquisa
27.31%
For enhancing the protection level of dynamic graph software watermarks and for the purpose of conducting the analysis which evaluates the effect of integrating two software protection techniques such as software watermarking and tamper proofing, constant encoding technique along with the enhancement through the idea of constant splitting is proposed. In this paper Thomborson technique has been implemented with the scheme of breaking constants which enables to encode all constants without having any consideration about their values with respect to the value of watermark tree. Experimental analysis which have been conducted and provided in this paper concludes that the constant encoding process significantly increases the code size, heap space usage, and execution time, while making the tamper proofed code resilient to variety of semantic preserving program transformation attacks.; Comment: 7 pages IEEE format, International Journal of Computer Science and Information Security, IJCSIS December 2009, ISSN 1947 5500, http://sites.google.com/site/ijcsis/

Non-blind watermarking of network flows

Houmansadr, Amir; Kiyavash, Negar; Borisov, Nikita
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 10/03/2012
Relevância na Pesquisa
17.64%
Linking network flows is an important problem in intrusion detection as well as anonymity. Passive traffic analysis can link flows but requires long periods of observation to reduce errors. Active traffic analysis, also known as flow watermarking, allows for better precision and is more scalable. Previous flow watermarks introduce significant delays to the traffic flow as a side effect of using a blind detection scheme; this enables attacks that detect and remove the watermark, while at the same time slowing down legitimate traffic. We propose the first non-blind approach for flow watermarking, called RAINBOW, that improves watermark invisibility by inserting delays hundreds of times smaller than previous blind watermarks, hence reduces the watermark interference on network flows. We derive and analyze the optimum detectors for RAINBOW as well as the passive traffic analysis under different traffic models by using hypothesis testing. Comparing the detection performance of RAINBOW and the passive approach we observe that both RAINBOW and passive traffic analysis perform similarly good in the case of uncorrelated traffic, however, the RAINBOW detector drastically outperforms the optimum passive detector in the case of correlated network flows. This justifies the use of non-blind watermarks over passive traffic analysis even though both approaches have similar scalability constraints. We confirm our analysis by simulating the detectors and testing them against large traces of real network flows.

Towards a provably resilient scheme for graph-based watermarking

Bento, Lucila M. S.; Boccardo, Davidson; Machado, Raphael C. S.; de Sá, Vinícius G. Pereira; Szwarcfiter, Jayme L.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Relevância na Pesquisa
17.31%
Digital watermarks have been considered a promising way to fight software piracy. Graph-based watermarking schemes encode authorship/ownership data as control-flow graph of dummy code. In 2012, Chroni and Nikolopoulos developed an ingenious such scheme which was claimed to withstand attacks in the form of a single edge removal. We extend the work of those authors in various aspects. First, we give a formal characterization of the class of graphs generated by their encoding function. Then, we formulate a linear-time algorithm which recovers from ill-intentioned removals of $k \leq 2$ edges, therefore proving their claim. Furthermore, we provide a simpler decoding function and an algorithm to restore watermarks with an arbitrary number of missing edges whenever at all possible. By disclosing and improving upon the resilience of Chroni and Nikolopoulos's watermark, our results reinforce the interest in regarding it as a possible solution to numerous applications.; Comment: 44 pages, 6 figures. An extended abstract of this paper was published in Proceedings of the 39th International Workshop on Graph Theoretic Concepts in Computer Science (WG 2013), Lecture Notes in Computer Science 8165 (2013), 50-63

Graph Watermarks

Zhao, Xiaohan; Liu, Qingyun; Zhou, Lin; Zheng, Haitao; Zhao, Ben Y.
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 29/05/2015
Relevância na Pesquisa
28.09%
From network topologies to online social networks, many of today's most sensitive datasets are captured in large graphs. A significant challenge facing owners of these datasets is how to share sensitive graphs with collaborators and authorized users, e.g. network topologies with network equipment vendors or Facebook's social graphs with academic collaborators. Current tools can provide limited node or edge privacy, but require modifications to the graph that significantly reduce its utility. In this work, we propose a new alternative in the form of graph watermarks. Graph watermarks are small graphs tailor-made for a given graph dataset, a secure graph key, and a secure user key. To share a sensitive graph G with a collaborator C, the owner generates a watermark graph W using G, the graph key, and C's key as input, and embeds W into G to form G'. If G' is leaked by C,its owner can reliably determine if the watermark W generated for C does in fact reside inside G', thereby proving C is responsible for the leak. Graph watermarks serve both as a deterrent against data leakage and a method of recourse after a leak. We provide robust schemes for creating, embedding and extracting watermarks, and use analysis and experiments on large, real graphs to show that they are unique and difficult to forge. We study the robustness of graph watermarks against both single and powerful colluding attacker models...

A Comparison between Digital Image Watermarking in Tow Different Color Spaces Using DWT2

Khalili, Mehdi
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 20/06/2012
Relevância na Pesquisa
17.31%
A novel digital watermarking for ownership verification and image authentication applications using discrete wavelet transform (DWT) is proposed in this paper. Most previous proposed watermarking algorithms embed sequences of random numbers as watermarks. Here binary images are taken as watermark for embedding. In the proposed approach, the host image is converted into the YCbCr color space and then its Y channel decomposed into wavelet coefficients. The selected approximation coefficients are quantized and then their four least significant bits of the quantized coefficients are replaced by the watermark using LSB insertion technique. At last, the watermarked image is synthesized from the changed and unchanged DWT coefficients. The experiments show that the proposed approach provides extra imperceptibility and robustness against wavelet compression compared to the traditional embedding methods in RGB color space. Moreover, the proposed approach has no need of the original image to extract watermarks.; Comment: 5 pages, 4 Figures, 6 Tables. arXiv admin note: text overlap with arXiv:1007.5136 by other authors