Recover the tampered image based on VQ indexing

In this paper, a tampered image recovery scheme is proposed by creating an index table of the original image via vector quantization (VQ) and embedding it into the original image as a basis for recovery. In order to complete the goal of image authentication and recovery, Wong's watermarking scheme [P.W. Wong, N. Memon, Secret an public key image watermarking schemes for image authentication and ownership verification, IEEE Trans. Image Process 10 (10) (2001) 1593-1601] is employed to perform tamper detection. Wong's watermarking scheme can be used to accurately locate tampered regions. If an image has been tampered, the index table can be used to recover the tampered regions. The experimental results indicate that our scheme has the higher probability of image recovery. Besides, compared with Lee and Lin's I Dual watermark for image tamper detection and recovery, Pattern Recognition 41 (2008) 3497-3506] scheme, our scheme provides not only a better quality of recovered images but also better results at edge regions. (C) 2009 Elsevier B.V. All rights reserved

Privacy-preserving information hiding and its applications

The phenomenal advances in cloud computing technology have raised concerns about data privacy. Aided by the modern cryptographic techniques such as homomorphic encryption, it has become possible to carry out computations in the encrypted domain and process data without compromising information privacy. In this thesis, we study various classes of privacy-preserving information hiding schemes and their real-world applications for cyber security, cloud computing, Internet of things, etc. Data breach is recognised as one of the most dreadful cyber security threats in which private data is copied, transmitted, viewed, stolen or used by unauthorised parties. Although encryption can obfuscate private information against unauthorised viewing, it may not stop data from illegitimate exportation. Privacy-preserving Information hiding can serve as a potential solution to this issue in such a manner that a permission code is embedded into the encrypted data and can be detected when transmissions occur. Digital watermarking is a technique that has been used for a wide range of intriguing applications such as data authentication and ownership identification. However, some of the algorithms are proprietary intellectual properties and thus the availability to the general public is rather limited. A possible solution is to outsource the task of watermarking to an authorised cloud service provider, that has legitimate right to execute the algorithms as well as high computational capacity. Privacypreserving Information hiding is well suited to this scenario since it is operated in the encrypted domain and hence prevents private data from being collected by the cloud. Internet of things is a promising technology to healthcare industry. A common framework consists of wearable equipments for monitoring the health status of an individual, a local gateway device for aggregating the data, and a cloud server for storing and analysing the data. However, there are risks that an adversary may attempt to eavesdrop the wireless communication, attack the gateway device or even access to the cloud server. Hence, it is desirable to produce and encrypt the data simultaneously and incorporate secret sharing schemes to realise access control. Privacy-preserving secret sharing is a novel research for fulfilling this function. In summary, this thesis presents novel schemes and algorithms, including: • two privacy-preserving reversible information hiding schemes based upon symmetric cryptography using arithmetic of quadratic residues and lexicographic permutations, respectively. • two privacy-preserving reversible information hiding schemes based upon asymmetric cryptography using multiplicative and additive privacy homomorphisms, respectively. • four predictive models for assisting the removal of distortions inflicted by information hiding based respectively upon projection theorem, image gradient, total variation denoising, and Bayesian inference. • three privacy-preserving secret sharing algorithms with different levels of generality

Application and Theory of Multimedia Signal Processing Using Machine Learning or Advanced Methods

This Special Issue is a book composed by collecting documents published through peer review on the research of various advanced technologies related to applications and theories of signal processing for multimedia systems using ML or advanced methods. Multimedia signals include image, video, audio, character recognition and optimization of communication channels for networks. The specific contents included in this book are data hiding, encryption, object detection, image classification, and character recognition. Academics and colleagues who are interested in these topics will find it interesting to read

A Study of Image Authentication and Recovery

在目前的浮水印技術中，可以分為二類，一種是強韌型浮水印技術，可以抵抗有心人士的惡意攻擊且取出浮水印；另一種則是易碎型浮水印技術，這種技術也稱為影像認證，在影像傳輸的過程中，偵測影像是否遭受竄改。由於醫學影像、軍事影像等應用，需要很精確而不能有誤差的影像。基於對此應用的需求，在本論文中，我們首先提出了一套新的影像還原方法，其主要精神是將亂數序列之強韌型浮水印技術轉換成可還原的浮水印技術。將目前眾所周知的以亂數序列作為浮水印之強韌型浮水印技術為藏匿方法，配合Sobel邊緣偵測技術找出藏匿影像的邊緣之像素值且保留，最後取代原始影像的對應邊緣位置之像素值，而完成藏匿浮水印之影像。因為強韌型浮水印技術，本來就是利用其可接受影像處理破壞的特性，以達到保護其影像的安全，因此使用我們的方法，雖然損失一些浮水印的資訊，但由實驗結果可驗證其改變後的藏匿影像，沒有造成浮水印偵測的問題。如此一來，不僅可以驗證影像是否有藏匿浮水印，而且能夠達到還原原始影像之目的。 由於可還原的浮水印技術無法得知影像是否遭受竄改與無法承受任何的影像處理攻擊，因此在實際應用上限制其發展空間。且在影像認證技術蓬勃的發展中，主要研究都為了改善影像認證的強韌性與偵測能力，因此忽略影像重建這部份。所以本篇論文接著提出一套影像竄改偵測與重建的技術，首先將影像的像素值做隨機亂數的處理，使得全部的像素值重新排序，則可得到像素值對應藏匿位置之關係。亂數處理是為了避免讓有心人士，輕易就找出影像的重建資訊。接著將原始影像做向量量化編碼得到索引表，當作影像特徵再藏匿至原始影像中，爾後將藏匿的索引表取出即可用於重建影像毀損之部份。最後結合王學者的浮水印技術進行竄改偵測，達到影像認證與重建之目的。 總結我們所提出的方法，主要是利用王學者的浮水印技術，以準確的標示出被竄改的區域。若影像判定遭受竄改，則利用向量量化壓縮後的索引表重建影像被竄改的區域。雖然影像重建技術無法使得重建影像與原始影像完全一樣，但接收者可在收到影像後，找出竄改部份且立即重建該影像內容，使得重建後影像品質與原始影像很相似，便可節省影像重新傳輸的頻寬與時間。根據相關實驗結果證實，本論文所提出的第一個技術只需額外付出平均約5.61 K bytes很少的還原資訊即可達到影像還原的目的。此外在第二個技術中，我們的方法不僅增加影像特徵的藏匿次數，達到提升影像重建的機率，而且影像邊緣的部份亦有較好之重建品質。Today's watermarking techniques can be divided into two types. The first type is robust watermarking technique which can resist malicious attacks better. The second type is fragile watermarking technique, also called image authentication, can verify whether the image is tampered in the process of image transfer or not. There are some applications requires accurate images such as medical or military images which users need to employ original images. Based on those specific requirements, we proposed a scheme of image recovery. The first proposed scheme improves the robust digital watermarking technique based on random sequence into reversible watermarking technique. Therefore, this method will use the robust watermarking technique of the well-known random sequence as embedding approach. Sobel edge detection technique is employed to extract the pixel value of edges from the watermarked image. And the final watermarked image is produced by replace the original image corresponding to the pixel value of the edges for the purpose of embedding watermark. Because the robust watermarking technique can tolerate the image which is destroyed to protect the copyright, there is no watermarking examination problem although this approach causes some loss of watermark information according to the experiment result. Moreover, it can not only examine whether the image has embedded watermarks, but also restore the original image. Majority of researches related to the image authentication are mainly focusing on improving the robustness and the ability of tamper detection on image authentication. The practical application of restrictions on reversible watermarking technique, which can't tolerate any image processing attack, neither can tell whether the image is tampered or not. Nevertheless, image recovering is also an important issue. We proposed an image tamper detection and recovery method, which can recovery image effectively, especially for images with large tampered regions. First, a secret key is used to obtain a random sequence and determine where to embed watermarks on the basis of this random sequence. As a result, it is hard to find out the corresponding location of watermarks from embedded images. Later, through vector quantization, we create an index table as a basis for recovery and embed it in the original image. Finally, Wong's watermarking scheme is integrated to perform tamper detection and achieve image authentication and recovery. Summary of our method, Wong's watermarking scheme is employed to perform tamper detection. Wong's watermarking scheme can be used to accurately locate tampered regions. If an image has been tampered, the index table can be used to recover the tampered regions. Although the image recovery technique unable to restore the image completely, receiver can identify the tampered locations and recovery immediately, as it will save additional bandwidth to retransmit the image. According to the experiment results, the first method we propose only needs to pay 5.61 k bytes overheads in average for restoring original images. Besides, the second method has the higher probability of image recovery and our scheme provides not only a better quality of recovered images but also better results at edge regions.Acknowledgement i Abstract (in Chinese) ii Abstract (in English) iii Table of Contents v List of Tables vii List of Figures viii Chapter 1 Introduction 1 1.1 Thesis Motivation 1 1.2 Thesis Organization 5 Chapter 2 Backgrounds 6 2.1 Related Work on Reversible Watermarking Technique 6 2.1.1 Reversible watermarking techniques by applying data compression 8 2.1.2 Reversible watermarking techniques using difference expansion 9 2.1.3 Reversible watermarking techniques exploiting histogram modification 10 2.2 Related Work on Image Recovery Technique 11 Chapter 3 A Reversible Watermarking Technique Based on Random Sequence 16 3.1 Related Works 16 3.1.1 The Watermarking Technique Based on Random Sequence 17 3.1.2 Sobel Edge Detection 20 3.2 Our method 20 3.2.1 Watermark Embedding 21 3.2.2 Watermark Examination and Image Restoring 22 3.3 Experimental Results 24 3.4 Discussion and Summary 28 Chapter 4 Recover the Tampered Image Based on VQ Indexing 29 4.1 Related Works 29 4.1.1 Wong's Watermarking Scheme 30 4.1.1.1 Watermark Embedding 30 4.1.1.2 Watermark Extraction 33 4.1.2 Vector Quantization 34 4.2 The Proposed Scheme 35 4.2.1 VQ Index Embedding and Watermark Embedding 35 4.2.2 Watermark Extraction and Image Recovery 42 4.3 Experimental Results 45 4.4 Discussion and Summary 55 Chapter 5 Conclusions and Future Works 56 References 5