Invisible Watermark

1. Invisible Watermark By Elo Leung and Wing Wong CS 265 Section 2 Spring 2004

2. Table of Contents • Project Objectives • Watermarking in General • Attacks on Watermarks • Desired Characteristics of Invisible Watermarks • Spread Spectrum Watermarking • – Insert & Extract Watermark • Example • Advantages & Disadvantages • 8. Conclusion

3. Project Objectives • Analyze the spread spectrum watermarking algorithm • proposed by Cox et al. • Demonstrate the application of Cox’s algorithm • using a sample image file

4. Watermarking in General • the 3 components: • Watermark • Encoder • – watermark insertion • Decoder and Comparator • – watermark extraction and verification

5. Watermarking in General • the 3 components: • Watermark • Encoder • Decoder and Comparator Figure provided by Mohanty [2].

6. Watermarking in General • Uses 3 components: • Watermark • Encoder • Decoder and Comparator Figure provided by Mohanty [2].

7. Attacks on Watermark Figure provided by Cox et al. [1].

8. e.g. JPEG/MPEG Irreversible Data Loss Quality Degradation Attacks on Watermark

9. Attacks on Watermark Specific for images/videos rotation, translation, scaling, and cropping operations

10. analog-to-digital, digital-to-analog conversion, etc. Attacks on Watermark

11. Attacks on Watermark Rewatermarking

12. Desired Characteristics of Invisible Watermarks • Perceptually unnoticeable • Robust to common watermark attacks • Quality degradation upon removal of watermarks • Unambiguously identifies the owner of the digitized • medium (audio, video, or image).

13. Spread Spectrum Watermarking • Spread Spectrum Watermark = Invisible Watermark • Key: • Insert watermark at perceptually significant regions • Spread watermark throughout the data • **Data = audio, video, or image file

14. Spread Spectrum WatermarkingInsertion Process v'i = vi (1 + αxi) Figure provided by Mohanty [2].

15. sim(X, X*) = (X X*) sqrt (X X*) Spread Spectrum WatermarkingExtraction Process Figure provided by Mohanty [2].

16. Example (1) Original (2) Watermarked Differences of (1) & (2)

17. Advantages & Disadvantages • Advantages: • Not noticeable since the watermarks are spread out. • Can’t be removed without severe quality degradation • since watermarks are inserted at perceptually • significant regions. • Disadvantages: • Original watermark is required in the extraction process.

18. Conclusion • Spread spectrum watermarking: • Can be used for audio, video, and image files • Meets the desired characteristics of invisible • watermarks – unnoticeable, robust, unambiguous

19. References: [1]Ingemar J. Cox, et al., “Secure Spread Spectrum Watermarking for Multimedia”, IEEE Trans. on Image Processing, Vol. 6, No.12, Dec 1997, pp.1673-1687. [2]   Saraju P. Mohanty, “Digital Watermarking: A Tutorial Review”, Department of Computer Science and Engineering, University of South Florida. [3]   Peter Meerwald, “Digital Image Watermarking in the Wavelet Transform Domain”, Master’s Thesis, Department of Scientific Computing, University of Salzburg, Austria, January 2001. [4] http://www.cosy.sbg.ac.at/~pmeerw/Watermarking/source/

20. The End