Abbas Thesis

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Abbas Thesis

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  • i

    Steganoflage: A New Image Steganography Algorithm

    Abbas Cheddad B.Sc./ M.Sc.

    School of Computing & Intelligent Systems Faculty of Computing & Engineering

    University of Ulster A thesis submitted in partial fulfilment of the requirements for the degree of

    Doctor of Philosophy

    September, 2009

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    Table of Contents Table of Contents .......................................................................................................... iiList of Figures ................................................................................................................ vList of Tables .............................................................................................................. viii List of Acronyms .......................................................................................................... ix ACKNOWLEDGEMENTS .............................................................................................. xiAbstract ........................................................................................................................ xiiNotes on access to contents ..................................................................................... xiii Chapter 1: Introduction .................................................................................................. 11.1 Motivations and Research Problem ........................................................................... 21.2 Objectives of this thesis ............................................................................................. 31.3 Outline of this Thesis ................................................................................................. 4 Chapter 2: Digital Image Steganography ...................................................................... 62.1 Ancient Steganography ............................................................................................. 92.2 The Digital Era of Steganography ............................................................................ 102.3 Steganography Applications .................................................................................... 122.4 Steganography Methods .......................................................................................... 14

    2.4.1 Steganography exploiting the image format ...................................................... 162.4.2 Steganography in the image spatial domain ..................................................... 182.4.3 Steganography in the image frequency domain ................................................ 242.4.4 Adaptive steganography ................................................................................... 30

    2.5 Performance Analysis of Methods in the Literature with Recommendations ........... 372.6 Steganalysis ............................................................................................................ 452.7 Summary ................................................................................................................. 51 Chapter 3: Image Encryption Methods and Skin Tone Detection Algorithms ......... 533.1 Image Encryption Methods ...................................................................................... 533.2 Skin Tone Detection Methods .................................................................................. 61

    3.2.1 Orthogonal colour space (YCbCr) ...................................................................... 643.2.2 Log Opponent and HSV .................................................................................... 663.2.3 Basic N-rules RGB (NRGB) .............................................................................. 683.2.4 Other colour spaces .......................................................................................... 68

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    3.3 Summary ................................................................................................................. 69 Chapter 4: Steganoflage: Object-Oriented Image Steganography ........................... 704.1 Step 1: Payload Encryption (What to Embed?) ....................................................... 72

    4.1.1 A new image encryption algorithm .................................................................... 734.2. Step 2: Identifying Embedding Regions .................................................................. 764.3 Step 3: The Embedding .......................................................................................... 814.4 Summary ................................................................................................................. 90 Chapter 5: Implementation of Steganoflage ............................................................... 925.1 Development Environment ...................................................................................... 925.2 Architecture of Steganoflage ................................................................................... 925.3 Bridging PHP to MATLAB ........................................................................................ 935.4 Applications of Steganoflage ................................................................................... 97

    5.4.1 Combating digital forgery .................................................................................. 98Motivations ............................................................................................................................ 98Methodology ....................................................................................................................... 100

    5.4.2 Multilayer security for patients data storage and transmission ....................... 1065.4.3 Digital reconstruction of lost signals ................................................................ 107

    5.5 Summary ............................................................................................................... 111 Chapter 6: Experimental Results .............................................................................. 1126.1 Security Analysis of the Image Encryption Method ................................................ 112

    6.1.1 Key space analysis ......................................................................................... 1126.1.2 Key sensitivity analysis (malleability attack) .................................................... 1136.1.3 Adjacent pixels analysis .................................................................................. 1136.1.4 Randomness test / Distinguishing attack ........................................................ 116

    The Chi-square distribution .............................................................................................. 116Frequency test (monobit test) .......................................................................................... 117Runs test ............................................................................................................................. 120Cross-covariance sequence ............................................................................................ 121

    6.1.5 Differential analysis ......................................................................................... 1236.1.6 Other security issues ....................................................................................... 125

    6.2 Evaluation of Skin Tone Detection Algorithm ......................................................... 1316.3 Overall Robustness of Steganoflage ..................................................................... 139

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    6.3.1 Robustness against intentional and passive attacks ....................................... 1406.3.2 Steganalysis and visual perceptibility .............................................................. 1426.3.3 Limitations and merits ..................................................................................... 144

    6.4 Summary ............................................................................................................... 149 Chapter 7: Conclusion and Future Work .................................................................. 1507.1 Summary ............................................................................................................... 1507.2 Relation to Other Work .......................................................................................... 153

    7.2.1 Region-based image watermarking ................................................................. 1547.2.2 Self-embedding ............................................................................................... 155

    7.3 Future Work ........................................................................................................... 1557.3.1 Resilience to print-scan distortions (secure ID card) ....................................... 1567.3.2 Resilience to severe image lossy compression (iPhone) ................................ 1567.3.3 Tamperproof CCTV surveillance ..................................................................... 157

    7.4 Conclusion ............................................................................................................. 158 Appendix A: Bridging MATLAB to a Web Scripting Language ................................... 161Appendix B: Image Encryption ................................................................................... 162Appendix C: Self-Embedding Examples .................................................................... 164Appendix D: Key Sensitivity Analysis of the Image Encryption .................................. 168Appendix E: Dark Skin-Tone Detection ...................................................................... 170Appendix F: Lossy Embedding wi