In recent years, there are more and more researches on semi-fragile watermarking scheme which can resist JPEG compression. But, there are few researches focused on the recovery of semi-fragile watermarked image. Therefore, in this paper, we not only present a semi-fragile watermarking scheme which can resist JPEG compression but use the error correction code (Reed-Solomon Code) to recover the area being malicious manipulated. At first, we use the semi-fragile watermarking scheme proposed by Lin and Hsieh to detect the counterfeit under the JPEG compression [9]. Its main effect is to resist JPEG compression and to detect the attacked parts without the need of the original image. And then, we will introduce how we use RS code to recover the attacked parts being detected by the semi-fragile watermarking scheme. We use the scheme ¡§Interleaving¡¨ to spread the local pixels to the global area. Next, we encode to each little image block by RS code. The redundant symbols generated by RS code will be signed to be signature attached with the watermarked image. Finally, the receiver can use semi-fragile watermarking scheme to detect attacked part and use the information of the signature to decode these attacked parts. Additionally, we also discuss how to decrease the load of the signature, thus, it can not significant loading of the watermarked image.

This thesis presents a novel singular-value-based semi-fragile watermarking scheme for image content authentication with tampering localization. The proposed scheme first generates a secured watermark bit sequence by performing a logical "xor" operation on a content-based watermark and content-independent watermark, wherein the content-based watermark is generated by a singular-value-based watermark bit sequence that represents intrinsic algebraic image properties, and the content-independent watermark is generated by a private-key-based random watermark bit sequence. It next embeds the secure watermark in the approximation subband of each non-overlapping 4×4 block using the adaptive quantization method to generate the watermarked image. The image content authentication process starts with regenerating the secured watermark bit sequence following the same process mentioned in the secured watermark bit sequence generation. It then extracts a possibly embedded watermark using the parity of the quantization results from the probe image. Next, the authentication process constructs a binary error map, whose height and width are a quarter of those of the original image, using the absolute difference between the regenerated secured watermark and the extracted watermark. It finally computes two authentication measures (i.e., M1 and M2), with M1 measuring the overall similarity between the regenerated watermark and the extracted watermark, and M2 measuring the overall clustering level of the tampered error pixels. These two authentication measures are further seamlessly integrated in the authentication process to confirm the image content and localize any possible tampered areas. The extensive experimental results show that the proposed scheme outperforms four peer schemes and is capable of identifying intentional tampering, incidental modification, and localizing tampered regions.

In this dissertation, the methods of protection and authentication for digital images are presented. In the study of fragile image authentication, the method that can thwart the counterfeit attack is proposed in Chapter 2, and we analyze this method in order to prove the effect. In the study of semi-fragile image authentication, two image authentication methods with digital signature-based and digital watermark-based are presented in Chapter 3 and Chapter 4 respectively. These two methods can improve the disadvantages of related works, and the main contributions are: (1) can adjust the fragile degree by assigning the least authenticable bound of image and (2) the related theorems about the proposed methods are analyzed completely. Finally, a new issue and solution about semi-fragile image authentication are presented in Chapter 5. The main contributions of this method are: (1) only the spatial domain is adopted during feature generation and verification, making domain transformation process is unnecessary, (2) more reasonable non-malicious manipulated images (JPEG, JPEG2000 compressed and scaled images) than related studies can be authenticated, achieving a good trade-off of image authentication between fragile and robust under practical image processing, and (3) non-malicious manipulation is clearly defined to meet closely the requirements of sending them over the Internet or storing images.

Image and video quality evaluation is very important. In applications involving signal transmission, the Reduced- or No-Reference quality metrics are generally more practical than the Full-Reference metrics. Digital watermarking based quality evaluation emerges as a potential Reduced- or No-Reference quality metric, which estimates signal quality by assessing the degradation of the embedded watermark. Since the watermark contains a small amount of information compared to the cover signal, performing accurate signal quality evaluation is a challenging task. Meanwhile, the watermarking process causes signal quality loss. To address these problems, in this thesis, a framework for image and video quality evaluation is proposed based on semi-fragile and adaptive watermarking. In this framework, adaptive watermark embedding strength is assigned by examining the signal quality degradation characteristics. The "Ideal Mapping Curve" is experimentally generated to relate watermark degradation to signal degradation so that the watermark degradation can be used to estimate the quality of distorted signals. With the proposed framework, a quantization based scheme is first implemented in DWT domain. In this scheme, the adaptive watermark embedding strengths are optimized by iteratively testing the image degradation characteristics under JPEG compression. This iterative process provides high accuracy for quality evaluation. However, it results in relatively high computational complexity. As an improvement, a tree structure based scheme is proposed to assign adaptive watermark embedding strengths by pre-estimating the signal degradation characteristics, which greatly improves the computational efficiency. The SPIHT tree structure and HVS masking are used to guide the watermark embedding, which greatly reduces the signal quality loss caused by watermark embedding. Experimental results show that the tree structure based scheme can evaluate image and video quality with high accuracy in terms of PSNR, wPSNR, JND, SSIM and VIF under JPEG compression, JPEG2000 compression, Gaussian low-pass filtering, Gaussian noise distortion, H.264 compression and packet loss related distortion.

Image and video quality evaluation is very important. In applications involving signal transmission, the Reduced- or No-Reference quality metrics are generally more practical than the Full-Reference metrics. Digital watermarking based quality evaluation emerges as a potential Reduced- or No-Reference quality metric, which estimates signal quality by assessing the degradation of the embedded watermark. Since the watermark contains a small amount of information compared to the cover signal, performing accurate signal quality evaluation is a challenging task. Meanwhile, the watermarking process causes signal quality loss. To address these problems, in this thesis, a framework for image and video quality evaluation is proposed based on semi-fragile and adaptive watermarking. In this framework, adaptive watermark embedding strength is assigned by examining the signal quality degradation characteristics. The "Ideal Mapping Curve" is experimentally generated to relate watermark degradation to signal degradation so that the watermark degradation can be used to estimate the quality of distorted signals. With the proposed framework, a quantization based scheme is first implemented in DWT domain. In this scheme, the adaptive watermark embedding strengths are optimized by iteratively testing the image degradation characteristics under JPEG compression. This iterative process provides high accuracy for quality evaluation. However, it results in relatively high computational complexity. As an improvement, a tree structure based scheme is proposed to assign adaptive watermark embedding strengths by pre-estimating the signal degradation characteristics, which greatly improves the computational efficiency. The SPIHT tree structure and HVS masking are used to guide the watermark embedding, which greatly reduces the signal quality loss caused by watermark embedding. Experimental results show that the tree structure based scheme can evaluate image and video quality with high accuracy in terms of PSNR, wPSNR, JND, SSIM and VIF under JPEG compression, JPEG2000 compression, Gaussian low-pass filtering, Gaussian noise distortion, H.264 compression and packet loss related distortion.

Image and video quality evaluation is very important. In applications involving signal transmission, the Reduced- or No-Reference quality metrics are generally more practical than the Full-Reference metrics. Digital watermarking based quality evaluation emerges as a potential Reduced- or No-Reference quality metric, which estimates signal quality by assessing the degradation of the embedded watermark. Since the watermark contains a small amount of information compared to the cover signal, performing accurate signal quality evaluation is a challenging task. Meanwhile, the watermarking process causes signal quality loss. To address these problems, in this thesis, a framework for image and video quality evaluation is proposed based on semi-fragile and adaptive watermarking. In this framework, adaptive watermark embedding strength is assigned by examining the signal quality degradation characteristics. The "Ideal Mapping Curve" is experimentally generated to relate watermark degradation to signal degradation so that the watermark degradation can be used to estimate the quality of distorted signals. With the proposed framework, a quantization based scheme is first implemented in DWT domain. In this scheme, the adaptive watermark embedding strengths are optimized by iteratively testing the image degradation characteristics under JPEG compression. This iterative process provides high accuracy for quality evaluation. However, it results in relatively high computational complexity. As an improvement, a tree structure based scheme is proposed to assign adaptive watermark embedding strengths by pre-estimating the signal degradation characteristics, which greatly improves the computational efficiency. The SPIHT tree structure and HVS masking are used to guide the watermark embedding, which greatly reduces the signal quality loss caused by watermark embedding. Experimental results show that the tree structure based scheme can evaluate image and video quality with high accuracy in terms of PSNR, wPSNR, JND, SSIM and VIF under JPEG compression, JPEG2000 compression, Gaussian low-pass filtering, Gaussian noise distortion, H.264 compression and packet loss related distortion.

The ease of digital media modification and dissemination necessitates content protection beyond encryption. Information hidden as digital watermarks in multimedia enables protection mechanism in decrypted contents. The aims of this research are three-fold: (i) to investigate the strength and limitations of current watermarking schemes, (ii) to design and develop new schemes to overcome the limitations, and (iii) to evaluate the new schemes using application scenarios of copyright protection, tamper detection and authentication. We focus on geometrically robust watermarking and semi-fragile watermarking for digital images. Additionally, hybrid schemes that combine the strength of both robust and semi-fragile watermarks are studied. Robust watermarks are well suited for copyright protection because they stay intact with the image under various manipulations. We investigated two major approaches of robust watermarking. In the synchronization approach, we employed motion estimation for watermark resynchronization. We also developed a novel watermark resynchronization method that has low computational cost using scale normalization and flowline curvature. In another approach, we firstly analyzed and improved a blind watermark detection method. The new method reduces significantly the computational cost of its watermark embedding. Secondly, we created a geometric invariant domain using a combination of transforms, and adapted the blind watermark detection method that we improved. It totally eliminates the need of resynchronization in watermark detection, which is a very desirable achievement that can hardly be found in existing schemes. On the other hand, semi-fragile watermarks are good at content authentication because they can differentiate minor image enhancements from major manipulations. New capabilities of semi-fragile watermarks are identified. Then, we developed a semi-fragile watermarking method in wavelet domain that offers content authentication and tamper localization. Unlike others, our scheme overcomes a major challenge called cropping attack and provides approximate content recovery without resorting to an original image. Hybrid schemes combine robust and semi-fragile watermarks to offer deductive information in digital media forensics. We firstly carried out a pilot study by combining robust and fragile watermarks. Then, we performed a comparative analysis on two implementation methods of a hybrid watermarking scheme. The first method has the robust watermark and the fragile watermark overlapped while the second method uses non-overlapping robust and fragile watermarks. Based on the results of the comparative analysis, we merge our geometric invariant domain with our semi-fragile watermark to produce a hybrid scheme. This hybrid scheme fulfilled the copyright protection, tamper detection, and content authentication objectives when evaluated in an investigation scenario.

The dissertation investigates the issues of image authentication and tamper localization after general image processing operations – blurring, sharpening, rotation and JPEG compression. The dissertation consists of four parts including Introduction, 4 chapters, Conclusions, References. The introduction reveals the investigated problem, importance of the thesis and the object of research and describes the purpose and tasks of the paper, research methodology, scientific novelty, the practical significance of results examined in the paper and defended statements. The introduction ends in presenting the author’s publications on the subject of the defended dissertation, offering the material of made presentations in conferences and defining the structure of the dissertation. Chapter 1 revises used literature, analyzes competitive methods. The devastating effect of blur/sharpen methods on digital image matrices is shown. General pixel-wise tamper localization methods are completely inefficient after such casual processing. Block-wise methods demonstrate some resistance against blurring/sharpening, but no tamper localization with the resolution of up to one pixel is possible. There is clearly a need for a method, able to locate damaged pixels despite general image processing operations such as blurring or sharpening. Chapter 2 defines theoretical foundation for the proposed method. It is shown that phase of Fourier transform demonstrates invariance against blurring or sharpening... [to full text] / Disertacijoje nagrinėjamos atvaizdų apsaugos – autentiškumo užtikrinimo ir pažeidimų radimo, po bendrųjų vaizdo apdorojimo procedūrų – blukinimo, ryškinimo, pasukimo ar JPEG suspaudimo – problemos. Disertaciją sudaro įvadas, keturi skyriai, rezultatų apibendrinimas, naudotos literatūros ir autoriaus publikacijų disertacijos tema sąrašai. Įvadiniame skyriuje aptariama tiriamoji problema, darbo aktualumas, aprašomas tyrimų objektas, formuluojamas darbo tikslas bei uždaviniai, aprašoma tyrimų metodika, darbo mokslinis naujumas, darbo rezultatų praktinė reikšmė, ginamieji teiginiai. Įvado pabaigoje pristatomos disertacijos tema autoriaus paskelbtos publikacijos ir pranešimai konferencijose bei disertacijos struktūra. Pirmasis skyrius skirtas literatūros apžvalgai. Jame pateikta konkuruojančių metodų apžvalga. Parodomas globalus blukinimo/ryškinimo operacijų poveikis atvaizdo skaitmeninėms matricoms. Išsiaiškinama kodėl pikselių tikslumo metodai nėra atsparūs tokiam poveikiui. Kodėl blokiniai metodai demonstruoja dalinį atsparumą – bet jie nėra pajėgūs surasti vieno pažeisto pikselio. Parodomas aiškus poreikis metodo, tiek galinčio rasti pažeistus pikselius, tiek atsparaus bendroms vaizdo apdorojimo procedūroms, tokioms kaip blukinimas ar aštrinimas. Antrajame skyriuje pateiktas sukurto metodo teorinis pagrindimas. Įrodoma, kad Furjė fazė pasižymi atsparumu blukinimui ir ryškinimui. Tačiau iškyla sekanti problema dėl to, kad Furjė fazėje neįmanoma rasti konkretaus pikselio –... [toliau žr. visą tekstą]