Source: Signal Processing, Available online 28 November 2007

Authors: Yung-Kuei Chiang, Piyu Tsai

Report: Jiun-Lwen LiangDate: 2012/06/07

Steganography using overlapping codebook partition

Outline

2012/6/72

Introduction

The proposed scheme

1. codebook partitioning

2. embedding procedure

3. extracting procedure

Experimental results

Conclusions

Introductions

2012/6/73

Communications security over the Internet is becoming more and more critical because of the digitization of data and networking of communications.

The steganography using overlapping codebook partition is proposed to extend the hiding capacity of a cover image and preserve the quality of a stegoimage.

Introductions

2012/6/74

Jo and Kim proposed an index-based watermarking scheme.

Chang and Wu presented an adaptive VQ-based data hiding scheme which is based on a codeword grouping technique.

Related work - VQ

2012/6/75

Vector quantization (VQ) – Codebook generation

Codebook

Training Images

0

1

2

.

.

.

N-1

Codeword1

Codeword2

Codeword3

.

.

.

Codeword N

2012/6/76

Vector quantization (VQ) – Encoding

2 62 60 174 …

100 95 202 174 …

…

…

…

…

Codebook

Index table

Original Image

0(16, 200, …,

90)

1 (35, 22, …, 100)

2 (40, 255, …, 59)

.

.

.

.

.

.

254 (90, 102, …, 98)

255 (145, 16, …, 99)

Related work - VQ

2012/6/77

Vector quantization (VQ) – Decoding

2 62 60 174 …

100 95 202 174 …

…

…

…

…

0(16, 200, …,

90)

1 (35, 22, …, 100)

2 (40, 255, …, 59)

.

.

.

.

.

.

254 (90, 102, …, 98)

255 (145, 16, …, 99)

Codebook

Index table

VQ Coded Image

Related work - VQ

The proposed scheme

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Codebookpartition

The proposed scheme -codebook partitioning

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sort the SEDs of each codeword between all other codewordsfrom small to big

clustered into four-member sub-cluster ( summed SED < TH1)

clustered into single-member sub-cluster

clustered into three-member sub-cluster ( summed SED < TH2)

clustered into two-member sub-cluster ( summed SED < TH3)

The proposed scheme -codebook partitioning

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2

1

( , ) ( ) h h

i j ik jkk

SED C C c c

Codebook partition algorithm

Squared Euclidean Distance(SED)

Thresholds TH1, TH2, TH3

The proposed scheme -codebook partitioning

60 61 62 63 64 65 66 67

60 0 80 200 300 250 90 100 400

61 80 0 110 120 185 285 210 310

62 200 110 0 350 190 160 220 320

63 300 120 350 0 220 260 230 330

64 250 185 190 220 0 180 480 320

65 90 285 160 260 180 0 140 500

66 100 210 220 230 480 140 0 270

67 400 310 320 330 320 500 270 0

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TH1=4550+80+90+100=270

0+80+110+120=310

0+110+160+190=460

0+120+220+230=570

0+180+185+190=555

0+90+140+160=390

0+100+140+210=450

0+270+310+320=900

60 → 60,61,65,66

61 → 60,61,62,63

65 → 60,62,65,66

66 → 60,61,65,66

TH2=350

0+110+160=270

0+120+220=340

0+180+190=370

0+270+310=580

62 → 62,61,65

63 → 63,61,64

TH3=200

0+190=190

0+270=270

64→64,62

67 →67

Residual

The proposed scheme -embedding procedure

(four-member sub-cluster)

Member

order 0 1 2 3

Binary expression 00 01 10 11Codeword

index 208 199 202 209

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209 64 78

…. …. ….

…. …. ….

Index table

199

209

index

secrete message: 0 1 1 0 1 1 0 0 1 1 …

The proposed scheme -embedding procedure

(three-member sub-cluster)

199 64 78

…. …. ….

…. …. ….

Member order 0 1 2

Codeword index 64 71 66

Codeword index 75 78 67

index

64

78

Member order in

sub-cluster

Member order in

sub-cluster

Three-bit

Values

0 0 000

0 1 001

0 2 010

1 0 011

1 1 100

1 2 101

2 0 110

2 1 111

2 2 N/A2012/6/7 13

embed bits : 101

Secret bits valued at 5

Index table

71 67

The proposed scheme -embedding procedure

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member order 0 1 2 3

sub-cluster A 180 176 172 175

sub-cluster B 180 179 172 175

sub-cluster C 178 177 183 175

secrete bit: 01

175 64 78

…. …. ….

…. …. ….

179 64 78

…. …. ….

…. …. ….

Find the most similar one to the originalindex 175

The proposed scheme -Extracting procedure

199 71 67

…. …. ….

…. …. ….

Codeword index

208 199 202 209

Member order

0 1 2 3

Binary expression

00 01 10 11

2012/6/7 15

Index table Codeword index

… 199 … …

…

199

209

…

index

…

secrete bit : 01 codebook

The proposed scheme -Extracting procedure

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199 71 67

…. …. ….

…. …. ….

Member order in

sub-cluster

Member order in

sub-cluster

Three-bit

Values

0 0 000

0 1 001

0 2 010

1 0 011

1 1 100

1 2 101

2 0 110

2 1 111

2 2 N/A

Secret bits 101

Member order 0 1 2

Codeword index … 71 …

Codeword index … … 67

index

71

67

codebook

Index table

Experimental results

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(f) Gold

(1) IEEE (2) CCU (3) NUU

512X512 pixels 128X128 pixels

Experimental results(2/5)

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Original image

Embedded image

“IEEE” “CCU” “NUU”

Experimental results

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Experimental results

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Cover image(512×512)

Secret data(256×256=65536 bits)

Experimental results

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Secret data 256x256

Experimental results

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Conclusion

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This method increases the hiding capacity and still have the great image quality.