146 research outputs found
Robust image steganography method suited for prining = Robustna steganografska metoda prilagođena procesu tiska
U ovoj doktorskoj dizertaciji prezentirana je robustna steganografska metoda razvijena i
prilagođena za tisak. Osnovni cilj metode je pružanje zaštite od krivotvorenja ambalaže.
Zaštita ambalaže postiže se umetanjem više bitova informacije u sliku pri enkoderu, a potom
maskiranjem informacije kako bi ona bila nevidljiva ljudskom oku. Informacija se pri
dekoderu detektira pomoću infracrvene kamere. Preliminarna istraživanja pokazala su da u
relevantnoj literaturi nedostaje metoda razvijenih za domenu tiska. Razlog za takav
nedostatak jest činjenica da razvijanje steganografskih metoda za tisak zahtjeva veću količinu
resursa i materijala, u odnosu na razvijanje sličnih domena za digitalnu domenu. Također,
metode za tisak često zahtijevaju višu razinu kompleksnosti, budući da se tijekom
reprodukcije pojavljuju razni oblici procesiranja koji mogu kompromitirati informaciju u slici
[1]. Da bi se sačuvala skrivena informacija, metoda mora biti otporna na procesiranje koje se
događa tijekom reprodukcije.
Kako bi se postigla visoka razina otpornosti, informacija se može umetnuti unutar
frekvencijske domene slike [2], [3]. Frekvencijskoj domeni slike možemo pristupiti pomoću
matematičkih transformacija. Najčešće se koriste diskretna kosinusna transformacija (DCT),
diskretna wavelet transformacija (DWT) i diskretna Fourierova transformacija (DFT) [2], [4].
Korištenje svake od navedenih transformacija ima određene prednosti i nedostatke, ovisno o
kontekstu razvijanja metode [5]. Za metode prilagođene procesu tiska, diskretna Fourierova
transformacija je optimalan odabir, budući da metode bazirane na DFT-u pružaju otpornost
na geometrijske transformacije koje se događaju tijekom reprodukcije [5], [6].
U ovom istraživanju korištene su slike u cmyk prostoru boja. Svaka slika najprije je
podijeljena u blokove, a umetanje informacije vrši se za svaki blok pojedinačno. Pomoću
DFT-a, ???? kanal slikovnog bloka se transformira u frekvencijsku domenu, gdje se vrši
umetanje informacije. Akromatska zamjena koristi se za maskiranje vidljivih artefakata
nastalih prilikom umetanja informacije. Primjeri uspješnog korištenja akromatske zamjene za
maskiranje artefakata mogu se pronaći 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 označena
slika posjeduje ista vizualna svojstva kao i slika prije označavanja. U eksperimentalnom dijelu rada koristi se 1000 slika u cmyk prostoru boja. U digitalnom
okruženju provedeno je istraživanje otpornosti metode na slikovne napade specifične za
reprodukcijski proces - skaliranje, blur, šum, rotaciju i kompresiju. Također, provedeno je
istraživanje otpornosti metode na reprodukcijski proces, koristeći tiskane uzorke. Objektivna
metrika bit error rate (BER) korištena je za evaluaciju. Mogućnost optimizacije metode
testirala se procesiranjem slike (unsharp filter) i korištenjem error correction kodova (ECC).
Provedeno je istraživanje kvalitete slike nakon umetanja informacije. Za evaluaciju su
korištene objektivne metrike peak signal to noise ratio (PSNR) i structural similarity index
measure (SSIM). PSNR i SSIM su tzv. full-reference metrike. Drugim riječima, potrebne su i
neoznačena i označena slika istovremeno, kako bi se mogla utvrditi razina sličnosti između
slika [9], [10]. Subjektivna analiza provedena je na 36 ispitanika, koristeći 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.
Također, metoda se uistinu optimizirala korištenjem unsharp filtera i ECC-a. Kvaliteta slike
ostaje visoka bez obzira na umetanje informacije, što su potvrdili rezultati eksperimenata s
objektivnim metrikama i subjektivna analiza
Data Hiding and Its Applications
Data hiding techniques have been widely used to provide copyright protection, data integrity, covert communication, non-repudiation, and authentication, among other applications. In the context of the increased dissemination and distribution of multimedia content over the internet, data hiding methods, such as digital watermarking and steganography, are becoming increasingly relevant in providing multimedia security. The goal of this book is to focus on the improvement of data hiding algorithms and their different applications (both traditional and emerging), bringing together researchers and practitioners from different research fields, including data hiding, signal processing, cryptography, and information theory, among others
Digital watermarking and novel security devices
EThOS - Electronic Theses Online ServiceGBUnited Kingdo
Information embedding and retrieval in 3D printed objects
Deep learning and convolutional neural networks have become the main tools of computer vision. These techniques are good at using supervised learning to learn complex representations from data. In particular, under limited settings, the image recognition model now performs better than the human baseline. However, computer vision science aims to build machines that can see. It requires the model to be able to extract more valuable information from images and videos than recognition. Generally, it is much more challenging to apply these deep learning models from recognition to other problems in computer vision.
This thesis presents end-to-end deep learning architectures for a new computer vision field: watermark retrieval from 3D printed objects. As it is a new area, there is no state-of-the-art on many challenging benchmarks. Hence, we first define the problems and introduce the traditional approach, Local Binary Pattern method, to set our baseline for further study. Our neural networks seem useful but straightfor- ward, which outperform traditional approaches. What is more, these networks have good generalization. However, because our research field is new, the problems we face are not only various unpredictable parameters but also limited and low-quality training data.
To address this, we make two observations: (i) we do not need to learn everything from scratch, we know a lot about the image segmentation area, and (ii) we cannot know everything from data, our models should be aware what key features they
should learn. This thesis explores these ideas and even explore more. We show how to use end-to-end deep learning models to learn to retrieve watermark bumps and tackle covariates from a few training images data. Secondly, we introduce ideas from synthetic image data and domain randomization to augment training data and understand various covariates that may affect retrieve real-world 3D watermark bumps. We also show how the illumination in synthetic images data to effect and even improve retrieval accuracy for real-world recognization applications
Copyright protection of scalar and multimedia sensor network data using digital watermarking
This thesis records the research on watermarking techniques to address the issue of copyright protection of the scalar data in WSNs and image data in WMSNs, in order to ensure that the proprietary information remains safe between the sensor nodes in both. The first objective is to develop LKR watermarking technique for the copyright protection of scalar data in WSNs. The second objective is to develop GPKR watermarking technique for copyright protection of image data in WMSN
Dynamic block encryption with self-authenticating key exchange
One of the greatest challenges facing cryptographers is the mechanism used
for key exchange. When secret data is transmitted, the chances are that there
may be an attacker who will try to intercept and decrypt the message. Having
done so, he/she might just gain advantage over the information obtained, or
attempt to tamper with the message, and thus, misguiding the recipient.
Both cases are equally fatal and may cause great harm as a consequence.
In cryptography, there are two commonly used methods of exchanging secret
keys between parties. In the first method, symmetric cryptography, the key is
sent in advance, over some secure channel, which only the intended recipient
can read. The second method of key sharing is by using a public key exchange
method, where each party has a private and public key, a public key is shared
and a private key is kept locally. In both cases, keys are exchanged between
two parties.
In this thesis, we propose a method whereby the risk of exchanging keys
is minimised. The key is embedded in the encrypted text using a process
that we call `chirp coding', and recovered by the recipient using a process
that is based on correlation. The `chirp coding parameters' are exchanged
between users by employing a USB flash memory retained by each user. If the
keys are compromised they are still not usable because an attacker can only
have access to part of the key. Alternatively, the software can be configured
to operate in a one time parameter mode, in this mode, the parameters
are agreed upon in advance. There is no parameter exchange during file
transmission, except, of course, the key embedded in ciphertext.
The thesis also introduces a method of encryption which utilises dynamic blocks, where the block size is different for each block. Prime numbers are
used to drive two random number generators: a Linear Congruential Generator
(LCG) which takes in the seed and initialises the system and a Blum-Blum
Shum (BBS) generator which is used to generate random streams to encrypt
messages, images or video clips for example. In each case, the key created is
text dependent and therefore will change as each message is sent.
The scheme presented in this research is composed of five basic modules. The
first module is the key generation module, where the key to be generated is
message dependent. The second module, encryption module, performs data
encryption. The third module, key exchange module, embeds the key into
the encrypted text. Once this is done, the message is transmitted and the
recipient uses the key extraction module to retrieve the key and finally the
decryption module is executed to decrypt the message and authenticate it.
In addition, the message may be compressed before encryption and decompressed
by the recipient after decryption using standard compression tools
Robust digital image watermarking algorithms for copyright protection
Digital watermarking has been proposed as a solution to the problem of resolving copyright ownership of multimedia data (image, audio, video). The work presented in this thesis is concerned with the design of robust digital image watermarking algorithms for copyright protection.
Firstly, an overview of the watermarking system, applications of watermarks as well as the survey of current watermarking algorithms and attacks, are given. Further, the implementation of feature point detectors in the field of watermarking is introduced. A new class of scale invariant feature point detectors is investigated and it is showed that they have excellent performances required for watermarking.
The robustness of the watermark on geometrical distortions is very important issue in watermarking. In order to detect the parameters of undergone affine transformation, we propose an image registration technique which is based on use of the scale invariant feature point detector. Another proposed technique for watermark synchronization is also based on use of scale invariant feature point detector. This technique does not use the original image to determine the parameters of affine transformation which include rotation and scaling. It is experimentally confirmed that this technique gives excellent results under tested geometrical distortions.
In the thesis, two different watermarking algorithms are proposed in the wavelet domain. The first algorithm belongs to the class of additive watermarking algorithms which requires the presence of original image for watermark detection. Using this algorithm the influence of different error correction codes on the watermark robustness is investigated. The second algorithm does not require the original image for watermark detection. The robustness of this algorithm is tested on various filtering and compression attacks. This algorithm is successfully combined with the aforementioned synchronization technique in order to achieve the robustness on geometrical attacks.
The last watermarking algorithm presented in the thesis is developed in complex wavelet domain. The complex wavelet transform is described and its advantages over the conventional discrete wavelet transform are highlighted. The robustness of the proposed algorithm was tested on different class of attacks. Finally, in the thesis the conclusion is given and the main future research directions are suggested
Tatouage robuste d’images imprimées
Invisible watermarking for ID images printed on plastic card support is a challenging problem that interests the industrial world. In this study, we developed a watermarking algorithm robust to various attacks present in this case. These attacks are mainly related to the print/scan process on the plastic support and the degradations that an ID card can encounter along its lifetime. The watermarking scheme operates in the Fourier domain as this transform has invariance properties against global geometrical transformations. A preventive method consists of pre-processing the host image before the embedding process that reduces the variance of the embeddable vector. A curative method comprises two counterattacks dealing with blurring and color variations. For a false alarm probability of 10⁻⁴, we obtained an average improvement of 22% over the reference method when only preventative method is used. The combination of the preventive and curative methods leads to a detection rate greater than 99%. The detection algorithm takes less than 1 second for a 512×512 image with a conventional computer, which is compatible with the industrial application in question.Le tatouage invisible d’images d’identité imprimées sur un support en plastique est un problème difficile qui intéresse le monde industriel. Dans cette étude, nous avons développé un algorithme de tatouage robuste aux diverses attaques présentes dans ce cas. Ces attaques sont liées aux processus d’impression/numérisation sur le support plastique ainsi qu’aux dégradations qu’une carte plastique peut rencontrer le long de sa durée de vie. La méthode de tatouage opère dans le domaine de Fourier car cette transformée présente des propriétés d’invariances aux attaques géométriques globales. Une méthode préventive consiste en un prétraitement de l’image originale avant le processus d’insertion qui réduit la variance du vecteur support de la marque. Une méthode corrective comporte deux contre-attaques corrigeant le flou et les variations colorimétriques. Pour une probabilité de fausse alarme de 10⁻⁴, nous avons obtenu une amélioration moyenne de 22% par rapport à la méthode de référence lorsque seule la méthode préventive est utilisée. La combinaison de la méthode préventive avec la méthode corrective correspond à un taux de détection supérieur à 99%. L’algorithme de détection prends moins de 1 seconde pour à une image de 512×512 pixels avec un ordinateur classique ce qui est compatible avec l’application industrielle visée
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