Colored Watermarking Technology Based on Visual Cryptography

Author: Hsien-Chu Wu , Chwei-Shyong Tsai , Shu-Chuan Huang Speaker: Shu-Chuan Huang Date: May 4 , 2005

Outline

• Introduction

• The proposed method

• Experimental results

• Conclusions

Introduction

• Watermarking Technology

• Colored Visual Cryptography

Watermarking Technology

primitive image

watermarkstego-image

Good digital watermarking :

1. Perceptual invisible

2. Security

3. Blindness

4. Multiple watermarks

5. Robustness

Colored Visual Cryptography

Colored Visual Cryptography (cont.)

Colored Visual Cryptography (cont.)

The proposed method

The primitive gray-level image “Lena” Colored watermark

The proposed method (cont.)

Random

The proposed method (cont.)

Range of mean value

Mask

[0, 63]

[64, 127]

[128, 191]

[192, 255]

Mean:186

The color Masks of four kinds of mean values

coding table

The proposed method (cont.)

Experimental Results

Share image 1 Share image 2

Experimental Results

The recovered image from two share images

Experimental Results (cont.)

( a ) The cropping attacked “Lena” ( b ) The recovered image from two share images of cropped “Lena”

Experimental Results (cont.)

( a ) The blurring attacked “Lena” ( b ) The recovered image from two share images of blurred “Lena”

Experimental Results (cont.)

( b ) The recovered image from two share images of sharpened “Lena”

( a ) The sharpening attacked “Lena”

Conclusions

• Provide high robustness by using Visual

Cryptography technique in Digital Watermarking.

• Keep the quality of primitive image.

Watermarking Technology

Based on BTC MethodAuthor: Hsien-Chu Wu, Chwei-Shyong Tsai, I-Su LeeSpeaker: I-Su LeeDate: May 4, 2005

Outline

Introduction

The Proposed method

Experimental results

Conclusions

Block Truncation Coding, BTC

221 212 189 177

213 194 182 184

192 179 187 199

179 186 200 169

512×512

Mean = (221+212+189+…+200+169)/16 = 191M1 = (221+212+213+194+192+199+200)/7 = 204M0 = (189+177+182+184+179+187+179+186+169)/9 = 181

<191 0

>191 1

1 1 0 0

1 1 0 0

1 0 0 1

0 0 1 0

bitmap

BTC decompression

204 204 181 181

204 204 181 181

204 181 181 204

181 181 204 181

bitmap

<191 0

>191 1

0 181

1 204

1 1 0 0

1 1 0 0

1 0 0 1

0 0 1 0

Mean = (221+212+189+…+200+169)/16 = 191M1 = (221+212+213+194+192+199+200)/7 = 204M0 = (189+177+182+184+179+187+179+186+169)/9 = 181

The Proposed method

8-bit grayscale image

binary watermark

Codebook design

min distance

128×128cover-image

codebook

Codebook design (cont.)

codebook

codebook0

codebook1

0

1

Watermark Embedding

codebook0

codebook1

cover-image

binary watermark

0

1stego-image

cover-image

binary watermark

Watermark Extraction (cont.)

stego-image

codebook0

codebook1

0

1

binary watermark

Experimental results

(a) Lena (b) Girl (c) F16

(d) Pepper (e) Splash (f) Tiffany

Experimental results (cont.)

Cover-image stego-image (unit:dB)BTC compression i

mage (unit:dB)

Lena 33.41009155 33.69390363

Girl 37.79463397 37.91506876

F16 30.92604062 31.29763583

Peppers 33.07814946 33.49940908

Splash 36.76107951 37.12370245

Tiffany 33.01723640 33.67697558

Comparison results (PSNR)

Experimental results (cont.)

(a) cropping attack

watermark

bit correct rate

= 0.89063

watermark

bit correct rate

= 0.88672

(b) cropping attack

Experimental results (cont.)

bit correct rate

= 0.88964

bit correct rate

= 0.86230

watermark

watermark

(c) cropping attack

(d) cropping attack

Experimental results (cont.)

bit correct rate

= 0.92969

bit correct rate

= 0.86035

watermark

watermark

(e) sharpening attack

(f) blurring attack

Experimental results (cont.)

Cover image

Lena 0.89063 0.88672 0.88964 0.86230 0.92969 0.86035

Girl 0.88965 0.87891 0.89063 0.86133 0.91406 0.81641

F16 0.88574 0.88769 0.88672 0.86035 0.92188 0.84375

Peppers 0.88574 0.88672 0.88965 0.86230 0.92578 0.73730

Splash 0.88574 0.88672 0.88671 0.86328 0.91992 0.81152

Tiffany 0.85253 0.85351 0.85352 0.84766 0.93554 0.87890

Average 0.88167 0.88005 0.88281 0.85954 0.92448 0.82471

Correct rate of six kinds of attacked watermark

(a) cropping

attack

(b) cropping

attack

(c) cropping

attack

(d) cropping

attack

(f) sharpening

attack

(g) blurring

attack

Conclusions

The proposed method can embed watermark in compressed images directly.

It is simple and efficient to embed watermark in images with using BTC.

Stego-image has good image quality.