A chaos-based robust wavelet-domain watermarking algorithm

1. A chaos-based robust wavelet-domain watermarking algorithm Source: Chaos, Solitions and Fractals, Vol. 22, 2004, pp. 47-54. Authors: Zhao Dawei, Chen Guanrong, Liu Wenbo Speaker: Hao-Cheng Wang(王皓正) Date: 2004/9/22 NTIT

2. Outline • Introduction • Watermarking in the wavelet domain • DWT (Discrete Wavelet Transformation) • Chaos and its application to watermarking • The new watermarking algorithm • Watermark embedding • Watermark detection • Results and analysis • Conclusions • Comment NTIT

3. Watermarking in the wavelet domain • The digital watermarking technology includes • Spatial-domain • Transform-domain • DCT, DWT NTIT

4. LL1 HL1 LH1 HH1 DWT (Discrete Wavelet Transformation)(1/2) • 低頻(low frequency)：像素之間的變化小，影像較平滑，人眼的敏感度高． • LL1 • 高頻(high frequency)：像素之間的差異大，影像較粗糙、模糊，人眼的敏感度較低． • HH1 • 中頻：介於低頻與高頻之間． • HL1、LH1 NTIT

5. LL2 HL2 HL1 LL1 HL1 LH2 HH2 LH1 HH1 LH1 HH1 DWT (Discrete Wavelet Transformation)(2/2) NTIT

6. Chaos and its application to watermarking • Logistic map • Where • When , the map is in the chaotic state. • Where NTIT

7. Logistic map(1/3) • Example NTIT

8. Logistic map(2/3) • Example NTIT

9. Logistic map(3/3) • We will use the logistic map twice: • To generate a label sequence • To generate the watermark NTIT

10. The new watermarking algorithm • Apply the wavelet transform locally DWT 8×8 block Isub (128×128) Iori (256×256) Watermark embedding 8×8 block IDWT I’sub (128×128) I’ori (256×256) NTIT

11. 1 2 32 ……………….. ……………………………….. ……………………………….. ……………………………….. ……………………………….. 993 ……………………….. 1024 Watermark embedding(1/7) Original Image(256×256 pixels) NTIT

12. 33, 1023, 112, 36, 77……………96, 1, 64…………………….983, 124, 33 33 1023 112 96 1 64 ……………………………… Label Sequence (Length=256) Watermark embedding(2/7) (1) (2) NTIT

13. Watermark embedding(3/7) NTIT

14. LL3 HL3 HL2 LH3 HH3 HL1 LH2 HH2 LH1 HH1 Watermark embedding(4/7) DWT NTIT

15. Watermark embedding(5/7) Type 1 Type 2 [1, -1] 111110000110 01110010…… 11111-1-1-111 -111-1 NTIT

16. , i=1, 2, …, N Cband are the original wavelet coefficients C’band are the watermarked wavelet coefficients αis a global parameter accounting for the watermark strength w is the watermark signal N is the element number of subband HL1 or HH1 or LH1 {HL1, HH1, LH1} Watermark embedding(6/7) (1) (2) (3) NTIT

17. , i=1, 2, …, N Watermark embedding(7/7) NTIT

18. Watermark detection(1/2) • The detection method we use is similar to the method proposed in [1] • We adopt the Neyman-Pearson criterion to determine the threshold Tp [1] Barni M, Bartolini F. Improved wavelet-bsed watermarking through pixel-wise masking. IEEE Trans Image Processing 2001;10(5):789-91. NTIT

19. Watermark detection(2/2) (1) if ρ>T ρ: a watermark signal exists; otherwise, a watermark signal does not exist (2) see [1] for more details NTIT

20. Results and analysis(1/3) • Test images: “Lena” and “Barbara”(256×256 pixels) • α=6.0, iseq=0.1564 and iwm=0.4123 NTIT

21. Results and analysis(2/3) PSNR=39.30 NTIT

22. Results and analysis(3/3) • When we set α=1.0, or smaller, we cannot detect the watermark correctly NTIT

23. Robustness against various attacks • α=6, Pf=10-8, iseq=0.1564, iwm=0.4123 • Additive noise attacks • Gaussian noise • Salt and pepper noise • JPEG compression • Geometric manipulations • Cropping, resizing, rotation NTIT

24. Cropping NTIT

25. Resizing and rotation • Resizing • Zoom scale m • Zoom in (m>1) • Zoom out (m<1) • m >0.625 • Rotation • 25° NTIT

26. Conclusions • This scheme applies the wavelet transform locally, based on the chaotic logistic map, and embeds the watermark into the DWT domain. • Introduced a blind watermarking detection technique using the Neyman-Pearson criterion. • Highly robust against geometric attacks and signal processing operations and JPEG compression. NTIT

27. LL3 HL3 HL2 LH3 HH3 HL1 LH2 HH2 LH1 HH1 Comment(1/2) • 結合圖片的浮水印技術 c1 c1 mod 2 = 1 or 0 ? c1 ±1 111110000110 01110010…… NTIT

28. Comment(2/2) p1 p1 mod 2 = 1 or 0 ? p1 ±1 NTIT