NTIT1 A chaos-based robust wavelet- domain watermarking algorithm Source: Chaos, Solitions and Fractals, Vol. 22, 2004, pp 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 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．  LL 1 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．  HH 1 中頻：介於低頻與高頻之間．  HL 1 、 LH 1 LH 1 HH 1 HL 1 LL 1

NTIT 5 DWT (Discrete Wavelet Transformation)(2/2) LH 1 HH 1 HL 1 LL 1 LH 1 HH 1 HL 1 LH 2 HH 2 HL 2 LL 2

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

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 Watermark embedding I ori (256 × 256) I sub (128 × 128) DWT IDWT I’ sub (128 × 128) I’ ori (256 × 256) 8×8 block

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

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

NTIT 13 Watermark embedding(3/7)

NTIT 14 Watermark embedding(4/7) LH 1 HH 1 HL 1 LH 2 HH 2 HL 2 LH 3 HH 3 HL 3 LL 3 DWT

NTIT 15 Watermark embedding(5/7) Type …… Type 2 [1, -1]

NTIT 16 Watermark embedding(6/7), i=1, 2, …, N C band 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 HL 1 or HH 1 or LH 1 {HL1, HH1, LH1} (1) (2) (3)

NTIT 17 Watermark embedding(7/7), i=1, 2, …, N i … i wm (i) … w(i)w(i) … C band … C’ band …

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 T p [1] Barni M, Bartolini F. Improved wavelet-bsed watermarking through pixel- wise masking. IEEE Trans Image Processing 2001;10(5):

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

NTIT 20 Results and analysis(1/3) Test images: “Lena” and “Barbara”(256×256 pixels) α=6.0, i seq = and i wm =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, P f =10 -8, i seq =0.1564, i wm = 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 Comment(1/2) 結合圖片的浮水印技術 …… LH 1 HH 1 HL 1 LH 2 HH 2 HL 2 LH 3 HH 3 HL 3 LL 3 c1c1 c 1 mod 2 = 1 or 0 ? c 1 ±1

NTIT 28 Comment(2/2) p1p1 p 1 mod 2 = 1 or 0 ? p 1 ±1