23 research outputs found
Enhancing fragility of zero-based text watermarking utilizing effective characters list
Text is an important medium used for sharing information worldwide. For a text document, digital watermarking is an efficient way for copyright protection, authentication, tamper proofing, to name but a few. In this paper, a zero-based watermarking approach is proposed for document authentication and tamper detection. To enhance the fragility of watermark, the proposed text watermarking approach can be comfortably utilized â based on the Effective Characters List (ECL) for watermark generation. The ECL method is generated for English text zero-watermarking by maintaining the contents of the original document and constructing the watermark by formulating the smooth transition between the selected characters in the documents. The evaluation of the proposed watermarking approach is based on three famous watermarking attacks including deletion, insertion, and reordering with an accuracy of 80.76%, 80.36%, and 88.1%, respectively. For a fair evaluation, a comparison is put forth with a recent zero-based watermarking method - clearly showing that the proposed method outperforms existing with greater accuracy. © 2019, Springer Science+Business Media, LLC, part of Springer Nature
Multibiometric security in wireless communication systems
This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University, 05/08/2010.This thesis has aimed to explore an application of Multibiometrics to secured wireless communications. The medium of study for this purpose included Wi-Fi, 3G, and
WiMAX, over which simulations and experimental studies were carried out to assess the performance. In specific, restriction of access to authorized users only is provided by a technique referred to hereafter as multibiometric cryptosystem. In brief, the system is built upon a complete challenge/response methodology in order to obtain a high level of security on the basis of user identification by fingerprint and further confirmation by verification of the user through text-dependent speaker recognition.
First is the enrolment phase by which the database of watermarked fingerprints with
memorable texts along with the voice features, based on the same texts, is created by sending them to the server through wireless channel.
Later is the verification stage at which claimed users, ones who claim are genuine, are verified against the database, and it consists of five steps. Initially faced by the identification level, one is asked to first present oneâs fingerprint and a memorable word, former is watermarked into latter, in order for system to authenticate the fingerprint and verify the validity of it by retrieving the challenge for accepted user.
The following three steps then involve speaker recognition including the user
responding to the challenge by text-dependent voice, server authenticating the response, and finally server accepting/rejecting the user.
In order to implement fingerprint watermarking, i.e. incorporating the memorable word as a watermark message into the fingerprint image, an algorithm of five steps has been developed. The first three novel steps having to do with the fingerprint
image enhancement (CLAHE with 'Clip Limit', standard deviation analysis and
sliding neighborhood) have been followed with further two steps for embedding, and
extracting the watermark into the enhanced fingerprint image utilising Discrete
Wavelet Transform (DWT).
In the speaker recognition stage, the limitations of this technique in wireless
communication have been addressed by sending voice feature (cepstral coefficients)
instead of raw sample. This scheme is to reap the advantages of reducing the
transmission time and dependency of the data on communication channel, together
with no loss of packet. Finally, the obtained results have verified the claims
Segmentation, registration,and selective watermarking of retinal images
In this dissertation, I investigated some fundamental issues related to medical image
segmentation, registration, and watermarking. I used color retinal fundus images to
perform my study because of the rich representation of different objects (blood vessels,
microaneurysms, hemorrhages, exudates, etc.) that are pathologically important
and have close resemblance in shapes and colors. To attack this complex subject, I
developed a divide-and-conquer strategy to address related issues step-by-step and to
optimize the parameters of different algorithm steps.
Most, if not all, objects in our discussion are related. The algorithms for detection,
registration, and protection of different objects need to consider how to differentiate
the foreground from the background and be able to correctly characterize the
features of the image objects and their geometric properties.
To address these problems, I characterized the shapes of blood vessels in retinal
images and proposed the algorithms to extract the features of blood vessels. A tracing
algorithm was developed for the detection of blood vessels along the vascular network.
Due to the noise interference and various image qualities, the robust segmentation
techniques were used for the accurate characterization of the objectsĂ shapes and verification.
Based on the segmentation results, a registration algorithm was developed,
which uses the bifurcation and cross-over points of blood vessels to establish the correspondence between the images and derive the transformation that aligns the images.
A Region-of-Interest (ROI) based watermarking scheme was proposed for image authenticity.
It uses linear segments extracted from the image as reference locations for
embedding and detecting watermark. Global and locally-randomized synchronization
schemes were proposed for bit-sequence synchronization of a watermark. The scheme
is robust against common image processing and geometric distortions (rotation and
scaling), and it can detect alternations such as moving or removing of the image
content
Scale Invariant and Rotation Invariant Image Watermarking
The scheme proposed is an improved version of the image watermarking scheme in "Scale-Invariant Image Watermarking via Optimization Algorithm for Quantizing Randomized Statistics". The previous watermarking scheme was scale invariant but not rotation invariant. In this thesis we propose to modify the method by incorporating Zernike moment transformation to make it rotationally invariant, thus making it robust against synchronization attacks.Computer Science Departmen
Multibiometric security in wireless communication systems
This thesis has aimed to explore an application of Multibiometrics to secured wireless communications. The medium of study for this purpose included Wi-Fi, 3G, and WiMAX, over which simulations and experimental studies were carried out to assess the performance. In specific, restriction of access to authorized users only is provided by a technique referred to hereafter as multibiometric cryptosystem. In brief, the system is built upon a complete challenge/response methodology in order to obtain a high level of security on the basis of user identification by fingerprint and further confirmation by verification of the user through text-dependent speaker recognition. First is the enrolment phase by which the database of watermarked fingerprints with memorable texts along with the voice features, based on the same texts, is created by sending them to the server through wireless channel. Later is the verification stage at which claimed users, ones who claim are genuine, are verified against the database, and it consists of five steps. Initially faced by the identification level, one is asked to first present oneâs fingerprint and a memorable word, former is watermarked into latter, in order for system to authenticate the fingerprint and verify the validity of it by retrieving the challenge for accepted user. The following three steps then involve speaker recognition including the user responding to the challenge by text-dependent voice, server authenticating the response, and finally server accepting/rejecting the user. In order to implement fingerprint watermarking, i.e. incorporating the memorable word as a watermark message into the fingerprint image, an algorithm of five steps has been developed. The first three novel steps having to do with the fingerprint image enhancement (CLAHE with 'Clip Limit', standard deviation analysis and sliding neighborhood) have been followed with further two steps for embedding, and extracting the watermark into the enhanced fingerprint image utilising Discrete Wavelet Transform (DWT). In the speaker recognition stage, the limitations of this technique in wireless communication have been addressed by sending voice feature (cepstral coefficients) instead of raw sample. This scheme is to reap the advantages of reducing the transmission time and dependency of the data on communication channel, together with no loss of packet. Finally, the obtained results have verified the claims.EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Visual Privacy Protection Methods: A Survey
Recent advances in computer vision technologies have made possible the development of intelligent monitoring systems for video surveillance and ambient-assisted living. By using this technology, these systems are able to automatically interpret visual data from the environment and perform tasks that would have been unthinkable years ago. These achievements represent a radical improvement but they also suppose a new threat to individualâs privacy. The new capabilities of such systems give them the ability to collect and index a huge amount of private information about each individual. Next-generation systems have to solve this issue in order to obtain the usersâ acceptance. Therefore, there is a need for mechanisms or tools to protect and preserve peopleâs privacy. This paper seeks to clarify how privacy can be protected in imagery data, so as a main contribution a comprehensive classification of the protection methods for visual privacy as well as an up-to-date review of them are provided. A survey of the existing privacy-aware intelligent monitoring systems and a valuable discussion of important aspects of visual privacy are also provided.This work has been partially supported by the Spanish Ministry of Science and Innovation under project âSistema de visiĂłn para la monitorizaciĂłn de la actividad de la vida diaria en el hogarâ (TIN2010-20510-C04-02) and by the European Commission under project âcaring4U - A study on people activity in private spaces: towards a multisensor network that meets privacy requirementsâ (PIEF-GA-2010-274649). JosĂ© RamĂłn Padilla LĂłpez and Alexandros Andre Chaaraoui acknowledge financial support by the Conselleria d'EducaciĂł, FormaciĂł i OcupaciĂł of the Generalitat Valenciana (fellowship ACIF/2012/064 and ACIF/2011/160 respectively)
Robust image steganography method suited for prining = Robustna steganografska metoda prilagoÄena procesu tiska
U ovoj doktorskoj dizertaciji prezentirana je robustna steganografska metoda razvijena i
prilagoÄena za tisak. Osnovni cilj metode je pruĆŸanje zaĆĄtite od krivotvorenja ambalaĆŸe.
ZaĆĄtita ambalaĆŸe postiĆŸe se umetanjem viĆĄe bitova informacije u sliku pri enkoderu, a potom
maskiranjem informacije kako bi ona bila nevidljiva ljudskom oku. Informacija se pri
dekoderu detektira pomoÄu infracrvene kamere. Preliminarna istraĆŸivanja pokazala su da u
relevantnoj literaturi nedostaje metoda razvijenih za domenu tiska. Razlog za takav
nedostatak jest Äinjenica da razvijanje steganografskih metoda za tisak zahtjeva veÄu koliÄinu
resursa i materijala, u odnosu na razvijanje sliÄnih domena za digitalnu domenu. TakoÄer,
metode za tisak Äesto zahtijevaju viĆĄu razinu kompleksnosti, buduÄi da se tijekom
reprodukcije pojavljuju razni oblici procesiranja koji mogu kompromitirati informaciju u slici
[1]. Da bi se saÄuvala skrivena informacija, metoda mora biti otporna na procesiranje koje se
dogaÄa tijekom reprodukcije.
Kako bi se postigla visoka razina otpornosti, informacija se moĆŸe umetnuti unutar
frekvencijske domene slike [2], [3]. Frekvencijskoj domeni slike moĆŸemo pristupiti pomoÄu
matematiÄkih transformacija. NajÄeĆĄÄe se koriste diskretna kosinusna transformacija (DCT),
diskretna wavelet transformacija (DWT) i diskretna Fourierova transformacija (DFT) [2], [4].
KoriĆĄtenje svake od navedenih transformacija ima odreÄene prednosti i nedostatke, ovisno o
kontekstu razvijanja metode [5]. Za metode prilagoÄene procesu tiska, diskretna Fourierova
transformacija je optimalan odabir, buduÄi da metode bazirane na DFT-u pruĆŸaju otpornost
na geometrijske transformacije koje se dogaÄaju tijekom reprodukcije [5], [6].
U ovom istraĆŸivanju koriĆĄtene su slike u cmyk prostoru boja. Svaka slika najprije je
podijeljena u blokove, a umetanje informacije vrĆĄi se za svaki blok pojedinaÄno. PomoÄu
DFT-a, ???? kanal slikovnog bloka se transformira u frekvencijsku domenu, gdje se vrĆĄi
umetanje informacije. Akromatska zamjena koristi se za maskiranje vidljivih artefakata
nastalih prilikom umetanja informacije. Primjeri uspjeĆĄnog koriĆĄtenja akromatske zamjene za
maskiranje artefakata mogu se pronaÄi u [7] i [8]. Nakon umetanja informacije u svaki
slikovni blok, blokovi se ponovno spajaju u jednu, jedinstvenu sliku. Akromatska zamjena
tada mijenja vrijednosti c, m i y kanala slike, dok kanal k, u kojemu se nalazi umetnuta
informacija, ostaje nepromijenjen. Time nakon maskiranja akromatskom zamjenom oznaÄena
slika posjeduje ista vizualna svojstva kao i slika prije oznaÄavanja. U eksperimentalnom dijelu rada koristi se 1000 slika u cmyk prostoru boja. U digitalnom
okruĆŸenju provedeno je istraĆŸivanje otpornosti metode na slikovne napade specifiÄne za
reprodukcijski proces - skaliranje, blur, ĆĄum, rotaciju i kompresiju. TakoÄer, provedeno je
istraĆŸivanje otpornosti metode na reprodukcijski proces, koristeÄi tiskane uzorke. Objektivna
metrika bit error rate (BER) koriĆĄtena je za evaluaciju. MoguÄnost optimizacije metode
testirala se procesiranjem slike (unsharp filter) i koriĆĄtenjem error correction kodova (ECC).
Provedeno je istraĆŸivanje kvalitete slike nakon umetanja informacije. Za evaluaciju su
koriĆĄtene objektivne metrike peak signal to noise ratio (PSNR) i structural similarity index
measure (SSIM). PSNR i SSIM su tzv. full-reference metrike. Drugim rijeÄima, potrebne su i
neoznaÄena i oznaÄena slika istovremeno, kako bi se mogla utvrditi razina sliÄnosti izmeÄu
slika [9], [10]. Subjektivna analiza provedena je na 36 ispitanika, koristeÄi ukupno 144
uzorka slika. Ispitanici su ocijenjivali vidljivost artefakata na skali od nula (nevidljivo) do tri
(vrlo vidljivo).
Rezultati pokazuju da metoda posjeduje visoku razinu otpornosti na reprodukcijski proces.
TakoÄer, metoda se uistinu optimizirala koriĆĄtenjem unsharp filtera i ECC-a. Kvaliteta slike
ostaje visoka bez obzira na umetanje informacije, ĆĄto su potvrdili rezultati eksperimenata s
objektivnim metrikama i subjektivna analiza
Dynamical Systems
Complex systems are pervasive in many areas of science integrated in our daily lives. Examples include financial markets, highway transportation networks, telecommunication networks, world and country economies, social networks, immunological systems, living organisms, computational systems and electrical and mechanical structures. Complex systems are often composed of a large number of interconnected and interacting entities, exhibiting much richer global scale dynamics than the properties and behavior of individual entities. Complex systems are studied in many areas of natural sciences, social sciences, engineering and mathematical sciences. This special issue therefore intends to contribute towards the dissemination of the multifaceted concepts in accepted use by the scientific community. We hope readers enjoy this pertinent selection of papers which represents relevant examples of the state of the art in present day research. [...