40 research outputs found
Study and Implementation of Watermarking Algorithms
Water Making is the process of embedding data called a watermark into a multimedia object such that watermark can be detected or extracted later to make an assertion about the object. The object may be an audio, image or video. A copy of a digital image is identical to the original. This has in many instances, led to the use of digital content with malicious intent. One way to protect multimedia data against illegal recording and retransmission is to embed a signal, called digital signature or copyright label or watermark that authenticates the owner of the data. Data hiding, schemes to embed secondary data in digital media, have made considerable progress in recent years and attracted attention from both academia and industry. Techniques have been proposed for a variety of applications, including ownership protection, authentication and access control. Imperceptibility, robustness against moderate processing such as compression, and the ability to hide many bits are the basic but rat..
Image adaptive watermarking using wavelet transform
The availability of versatile multimedia processing software and the far-reaching coverage of the interconnected networks have facilitated flawless copying, manipulations and distribution of the digital multimedia (digital video, audio, text, and images). The ever-advancing storage and retrieval technologies have also smoothed the way for large-scale multimedia database applications. However, abuses of these facilities and technologies pose pressing threats to multimedia security management in general, and multimedia copyright protection and content integrity verification in particular. Although cryptography has a long history of application to information and multimedia security, the undesirable characteristic of providing no protection to the media once decrypted has limited the feasibility of its widespread use. For example, an adversary can obtain the decryption key by purchasing a legal copy of the media but then redistribute the decrypted copies of the original. In response to these challenges; digital watermarking techniques have been proposed in the last decade. Digital watermarking is the procedure whereby secret information (the watermark) is embedded into the host multimedia content, such that it is: (1) hidden, i.e., not perceptually visible; and (2) recoverable, even after the content is degraded by different attacks such as filtering, JPEG compression, noise, cropping etc. The two basic requirements for an effective watermarking scheme, imperceptibility and robustness, conflict with each other. The main focus of this thesis is to provide good tradeoff between perceptual quality of the watermarked image and its robustness against different attacks. For this purpose, we have discussed two robust digital watermarking techniques in discrete wavelet (DWT) domain. One is fusion based watermarking, and other is spread spectrum based watermarking. Both the techniques are image adaptive and employ a contrast sensitivity based human visual system (HVS) model. The HVS models give us a direct way to determine the maximum strength of watermark signal that each portion of an image can tolerate without affecting the visual quality of the image. In fusion based watermarking technique, grayscale image (logo) is used as watermark. In watermark embedding process, both the host image and watermark image are transformed into DWT domain where their coefficients are fused according to a series combination rule that take into account contrast sensitivity characteristics of the HVS. The method repeatedly merges the watermark coefficients strongly in more salient components at the various resolution levels of the host image which provides simultaneous spatial localization and frequency spread of the watermark to provide robustness against different attacks. Watermark extraction process requires original image for watermark extraction. In spread spectrum based watermarking technique, a visually recognizable binary image is used as watermark. In watermark embedding process, the host image is transformed into DWT domain. By utilizing contrast sensitivity based HVS model, watermark bits are adaptively embedded through a pseudo-noise sequence into the middle frequency sub-bands to provide robustness against different attacks. No original image is required for watermark extraction. Simulation results of various attacks are also presented to demonstrate the robustness of both the algorithms. Simulation results verify theoretical observations and demonstrate the feasibility of the digital watermarking algorithms for use in multimedia standards
Digital rights management (DRM) - watermark encoding scheme for JPEG images
The aim of this dissertation is to develop a new algorithm to embed a watermark in JPEG compressed images, using encoding methods. This encompasses the embedding of proprietary information, such as identity and authentication bitstrings, into the compressed material. This watermark encoding scheme involves combining entropy coding with homophonic coding, in order to embed a watermark in a JPEG image. Arithmetic coding was used as the entropy encoder for this scheme. It is often desired to obtain a robust digital watermarking method that does not distort the digital image, even if this implies that the image is slightly expanded in size before final compression. In this dissertation an algorithm that combines homophonic and arithmetic coding for JPEG images was developed and implemented in software. A detailed analysis of this algorithm is given and the compression (in number of bits) obtained when using the newly developed algorithm (homophonic and arithmetic coding). This research shows that homophonic coding can be used to embed a watermark in a JPEG image by using the watermark information for the selection of the homophones. The proposed algorithm can thus be viewed as a ‘key-less’ encryption technique, where an external bitstring is used as a ‘key’ and is embedded intrinsically into the message stream. The algorithm has achieved to create JPEG images with minimal distortion, with Peak Signal to Noise Ratios (PSNR) of above 35dB. The resulting increase in the entropy of the file is within the expected 2 bits per symbol. This research endeavor consequently provides a unique watermarking technique for images compressed using the JPEG standard.Dissertation (MEng)--University of Pretoria, 2008.Electrical, Electronic and Computer Engineeringunrestricte
Digital watermarking and novel security devices
EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Comparative evaluation of video watermarking techniques in the uncompressed domain
Thesis (MScEng)--Stellenbosch University, 2012.ENGLISH ABSTRACT: Electronic watermarking is a method whereby information can be imperceptibly
embedded into electronic media, while ideally being robust against common signal
manipulations and intentional attacks to remove the embedded watermark. This
study evaluates the characteristics of uncompressed video watermarking techniques
in terms of visual characteristics, computational complexity and robustness against
attacks and signal manipulations.
The foundations of video watermarking are reviewed, followed by a survey of
existing video watermarking techniques. Representative techniques from different
watermarking categories are identified, implemented and evaluated.
Existing image quality metrics are reviewed and extended to improve their performance
when comparing these video watermarking techniques. A new metric for
the evaluation of inter frame flicker in video sequences is then developed.
A technique for possibly improving the robustness of the implemented discrete
Fourier transform technique against rotation is then proposed. It is also shown that
it is possible to reduce the computational complexity of watermarking techniques
without affecting the quality of the original content, through a modified watermark
embedding method.
Possible future studies are then recommended with regards to further improving
watermarking techniques against rotation.AFRIKAANSE OPSOMMING: ’n Elektroniese watermerk is ’n metode waardeur inligting onmerkbaar in elektroniese
media vasgelê kan word, met die doel dat dit bestand is teen algemene manipulasies
en doelbewuste pogings om die watermerk te verwyder. In hierdie navorsing
word die eienskappe van onsaamgeperste video watermerktegnieke ondersoek
in terme van visuele eienskappe, berekeningskompleksiteit en weerstandigheid teen
aanslae en seinmanipulasies.
Die onderbou van video watermerktegnieke word bestudeer, gevolg deur ’n oorsig
van reedsbestaande watermerktegnieke. Verteenwoordigende tegnieke vanuit verskillende
watermerkkategorieë word geïdentifiseer, geïmplementeer en geëvalueer.
Bestaande metodes vir die evaluering van beeldkwaliteite word bestudeer en uitgebrei
om die werkverrigting van die tegnieke te verbeter, spesifiek vir die vergelyking
van watermerktegnieke. ’n Nuwe stelsel vir die evaluering van tussenraampie flikkering
in video’s word ook ontwikkel.
’n Tegniek vir die moontlike verbetering van die geïmplementeerde diskrete Fourier
transform tegniek word voorgestel om die tegniek se bestandheid teen rotasie
te verbeter. Daar word ook aangetoon dat dit moontlik is om die berekeningskompleksiteit
van watermerktegnieke te verminder, sonder om die kwaliteit van die
oorspronklike inhoud te beïnvloed, deur die gebruik van ’n verbeterde watermerkvasleggingsmetode.
Laastens word aanbevelings vir verdere navorsing aangaande die verbetering van
watermerktegnieke teen rotasie gemaak
Digital watermarking methods for data security and authentication
Philosophiae Doctor - PhDCryptology is the study of systems that typically originate from a consideration of the ideal circumstances under which secure information exchange is to take place. It involves the study of cryptographic and other processes that might be introduced for breaking the output of such systems - cryptanalysis. This includes the introduction of formal mathematical methods for the design of a cryptosystem and for estimating its theoretical level of securit
Digital watermark technology in security applications
With the rising emphasis on security and the number of fraud related crimes
around the world, authorities are looking for new technologies to tighten
security of identity. Among many modern electronic technologies, digital
watermarking has unique advantages to enhance the document authenticity.
At the current status of the development, digital watermarking technologies
are not as matured as other competing technologies to support identity authentication
systems. This work presents improvements in performance of
two classes of digital watermarking techniques and investigates the issue of
watermark synchronisation.
Optimal performance can be obtained if the spreading sequences are designed
to be orthogonal to the cover vector. In this thesis, two classes of
orthogonalisation methods that generate binary sequences quasi-orthogonal
to the cover vector are presented. One method, namely "Sorting and Cancelling"
generates sequences that have a high level of orthogonality to the
cover vector. The Hadamard Matrix based orthogonalisation method, namely
"Hadamard Matrix Search" is able to realise overlapped embedding, thus the
watermarking capacity and image fidelity can be improved compared to using
short watermark sequences. The results are compared with traditional
pseudo-randomly generated binary sequences. The advantages of both classes
of orthogonalisation inethods are significant.
Another watermarking method that is introduced in the thesis is based
on writing-on-dirty-paper theory. The method is presented with biorthogonal
codes that have the best robustness. The advantage and trade-offs of
using biorthogonal codes with this watermark coding methods are analysed
comprehensively. The comparisons between orthogonal and non-orthogonal
codes that are used in this watermarking method are also made. It is found
that fidelity and robustness are contradictory and it is not possible to optimise
them simultaneously.
Comparisons are also made between all proposed methods. The comparisons
are focused on three major performance criteria, fidelity, capacity and
robustness. aom two different viewpoints, conclusions are not the same. For
fidelity-centric viewpoint, the dirty-paper coding methods using biorthogonal
codes has very strong advantage to preserve image fidelity and the advantage
of capacity performance is also significant. However, from the power
ratio point of view, the orthogonalisation methods demonstrate significant
advantage on capacity and robustness. The conclusions are contradictory
but together, they summarise the performance generated by different design
considerations.
The synchronisation of watermark is firstly provided by high contrast
frames around the watermarked image. The edge detection filters are used
to detect the high contrast borders of the captured image. By scanning
the pixels from the border to the centre, the locations of detected edges
are stored. The optimal linear regression algorithm is used to estimate the
watermarked image frames. Estimation of the regression function provides
rotation angle as the slope of the rotated frames. The scaling is corrected by
re-sampling the upright image to the original size. A theoretically studied
method that is able to synchronise captured image to sub-pixel level accuracy
is also presented. By using invariant transforms and the "symmetric
phase only matched filter" the captured image can be corrected accurately
to original geometric size. The method uses repeating watermarks to form an
array in the spatial domain of the watermarked image and the the array that
the locations of its elements can reveal information of rotation, translation
and scaling with two filtering processes
Watermarking Technique for Multimedia Documents in the Frequency Domain
In order to secure and maintain the authenticity and integrity of multimedia documents, we use digital watermarking. This discipline can be applied to images, audios, and videos. For this reason, and to be independent of the nature of the signal composing the document to be watermarked, we will propose in this chapter two watermarking techniques, one for the audio and another for the image to watermark a video containing the two components audio and image. MDCT is combined with Watson model and a motion detection algorithm in the image watermarking technique and is combined with a psychoacoustic model to elaborate the audio watermarking technique. For the two techniques, the bits of the mark will be duplicated to increase the capacity of insertion and then inserted into the least significant bit (LSB). We will use an error correction code (Hamming) on the mark for more reliability in the detection phase. To highlight our experimental results point of view robustness and imperceptibility, we will compare the proposed techniques with some other existing techniques