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Title: Digital image authentication
Author: Li, Yue
ISNI:       0000 0004 2690 821X
Awarding Body: University of Warwick
Current Institution: University of Warwick
Date of Award: 2009
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Due to the fast growth of digital technology, daily activities can be easily captured and saved in digital images, and then transmitted via the Internet. Therefore, the huge amount of digital images need to be protected through authentication techniques. This thesis is concerned with digital image authentication (DIA) techniques used for anti-falsification, copyright protection and access control. DIA techniques can be generally categorised into data-hiding-based digital image authentication (DHBDIA) techniques and non-data-hiding-based digital image authentication (NDHBDIA) techniques, which are both studied in this thesis. DHBDIA techniques, which are also called watermarking schemes, realise image authentication by imperceptibly embedding a piece of authentication information into images. In this thesis, three watermarking schemes are proposed to serve different purposes. To improve the performance of current clustering-based watermarking schemes, an expandable progressive exponential clustering (EPEC)-based watermarking scheme is proposed, which embeds secret data in the host image by progressively and exponentially clustering the colour intensities in the spatial domain, expanding the cluster table under predetermined constraints and substituting the intensities in the same clusters. This scheme strikes a better balance between embedding capacity and embedding distortion than traditional clustering-based watermarking schemes. To enhance the security of current quantisation-based watermarking schemes, an adaptive quantisation index modulation (AQIM)-based watermarking scheme is proposed, which adaptively modifies the quantised values in the embedding phase, consequently preserving the histogram of the image and closes the security gap. For the image authentication, a repetitive index modulation (RIM)-based watermarking scheme is proposed to set up a non-deterministic dependence among pixels. This scheme achieves higher security and lower distortion than traditional LSB-based watermarking schemes. Meanwhile, to study the applicability of DHBDIA techniques, a multifunction digital image authentication system for medical image management on PACSs is proposed to perform three different security assurance functions, namely role-based access control, patient’s medical information integration with mammograms and forgery detection. In the study of the NDHBDIA techniques, a colour-decoupled photo response non-uniformity (CD-PRNU) is devised to serve as a camera fingerprint for both source camera identification and content integrity verification. In the image acquisition process, colour filtering and interpolation are two important operations that introduce large amounts of noise, which are not included in the traditional PRNU definition. The proposed CD-PRNU extends the traditional photo response non-uniformity (PRNU) extraction model by including such types of noise. As a result, the CD-PRNU is more accurate and effective in camera identification and content integrity verification. The main feature of the proposed CD-PRNU extraction algorithm is that it can separate physical colour components and artificial colour components without the prior knowledge about the Colour Filter Array (CFA) and then extract the PRNU from each individual colour channel, thus preventing interpolation noise of artificial components from diffusing into the sensor pattern noise of the physical colour components.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available
Keywords: TA Engineering (General). Civil engineering (General)