摘要
在現今，發展一個系統，防止非法竄改和複製是非常重要任務，數位浮水印也似乎是多數地方之解決辦法，至今數位浮水印已經公開眾多演算法，多半也只是用於版權保護，至於其他安全保護，如影像認證服務，數位浮水印仍然存在許多問題有待解決。
最近一些研究所提演算法，不只能夠偵測到竄改位置，也能夠盡可能恢復原來資訊，如Chan and Chang (2007)提倡一個基於錯誤更正碼之影像認證機制，嘗試解決以上問題，多數情形都有不錯表現，但是卻包含一個安全漏洞。
本論文提倡一個基於錯誤更正碼影像認證演算法，不只能夠偵測到竄改位置，也能夠回復原來資訊，達到接受品質，且避免了Chan and Chang安全漏洞，再者本論文進一步提倡改良式modified prediction，再提升影像認證演算法之回復品質。
關鍵字：影像認證，竄改偵測，竄改回復，漢明碼ABSTRACT
In this context, it is important to develop systems for protection against duplication, copyright, and the authentication of content. Watermarking seems to be an alternative solution for intensifying the security of multimedia documents. Until now, the majority of publications in the field of watermarking mainly involve the copyrighting of still images. Other security services, such as image content authentication, are still peripheral, and many fundamental questions remain.
Recently, there existed some schemes that not only tried to localize tampered areas but also tried to restore a rough approximation of the damaged areas. Chan and Chang (2007) proposed a new scheme by using the Hamming code. This effectively detected and eliminated burst bit errors and the recovered pixels in detailed areas and could actually gain very high clarity. In this thesis, the potential weakness of the Chan-Chang scheme will be analyzed and the experimental results will show that a security problem does exist. Therefore, in order to benefit from the excellent advantages of the Chan-Chang scheme, it is worthwhile to propose an improved scheme based on the Hamming code that will enhance security. The improved scheme not only overcomes the potential security weakness of the Chan-Chang scheme but also takes advantage of and enhances the property of the (7,4) Hamming code rule.
Furthermore, the experimental results of adopting modified prediction are somewhat better than that of the original pixel prediction scheme of JPEG-LS. The experimental results show that the proposed scheme can withstand the noise-adding and tampering attacks. Moreover, performances of detecting and recovering are of high accuracy and of good quality. It is worthwhile to note that the ability of the lossless image remedy is analyzed under different tampered sizes and transmission errors.
Keywords: Image authentication; Tampering proof; Tamper remedy; Hamming code.TABLE OF CONTENTS
誌謝辭 I
摘要 II
Abstract III
Table of Contents IV
List of Figures VII
List of Tables IX
Chapter 1. Introduction 1
1.1. Motivation 1
1.2. Image authentication 2
1.3. Copyright watermarking 4
1.3.1. Classification of watermarking 4
1.3.2. Classification of imitations 6
1.3.3. Properties of copyright watermarking 6
1.4. Steganography 8
1.5. Error correcting codes 12
1.5.1. Linear codes 12
1.5.2. CRC codes 14
1.5.3. Weight distribution 15
1.5.4. Hamming Distance 15
1.5.5. Bit error rate (ε) 17
1.5.6. Probability of uncorrected error (Puc) 18
1.5.7. Probability of undetected error (Pud) 19
1.5.8. Well-designed code 20
1.6. Contribution 21
1.7. Organization of this thesis 22
Chapter 2. Previous work 23
2.1. Relative research 23
2.2. The Chan-Chang scheme 28
2.2.1. Embedding procedure of the Chan-Chang scheme 28
2.2.2. Detecting procedure of the Chan-Chang scheme 31
2.2.3. Recovering procedure of the Chan-Chang scheme 33
2.2.4. Security analysis of the Chan-Chang scheme 36
Chapter 3. The proposed scheme 41
3.1. Selection of error correcting codes 41
3.2. The proposed algorithm for image authentication 45
3.2.1. The embedding procedure 45
3.2.2. The detection procedure 47
3.2.3. The recovery procedure 49
3.3. Experimental results and discussions for image authentication 51
3.3.1. Noise-adding Attack 53
3.3.2. Tampering attack 54
3.3.3. Discussions 59
Chapter 4. The new Algorithm for Region of Interest (ROI) authentication 66
4.1. ROI authentication 66
4.2. The proposed algorithm for ROI authentication 67
4.2.1. The embedding procedure 70
4.2.2. The detecting procedure 73
4.2.3. The correcting procedure 74
4.3. Experimental results and discussions 75
4.3.1. Experimental results 75
4.3.2. Discussions 82
Chapter 5. Conclusions 85
APPENDIX A: The embedding algorithm of chapter 3 in matlab 87
APPENDIX B: The detecting and correcting algorithm of chapter 3 in matlab 89
References 98
INDEX 10
