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High-capacity image hiding scheme based on vector quantizationAuthors: Yu-Chen HuSource: Pattern Recognition, vol. 39, pp. 1715-1724, 2006Speaker: Shu-Fen Chiou(邱淑芬 )Date: 2006/10/19

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Outline

Introduction Proposed method Experimental results Conclusion Comment

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Introduction

This method is hiding multiple secret images into a host image of the same size.

The proposed scheme provides a higher hiding capacity.

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Hiding bits

1

log/ 2max hw

Nkhwsnor c

2753.1

1512512

128log16/5125124 2max

r

sno: total number of secret images

Nc: the size of VQ codebook

k: the vector dimension

rmax: The maximal number of modified bits

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Training codebook

.2 e with valu imagehost

in the pixeleach of bits last

thereplacingby generated be

can imagehost modified The

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max

'

max rH

r

H

'HH

10110001 10110001 10110001 10110011

01100010 01101010 01100000 01100010

00111111 00111111 00111111 00111101

10000000 10011100 10110000 10011000

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max

)10(22

2max

r

r

10110010 10110010 10110010 10110010

01100010 01100010 01100010 01100010

00111110 00111110 00111110 00111110

10000010 10000010 10000010 10000010

'H

Random seed rs

Codebook is sorted by mean values of codewords

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VQ

Original image Index table

51 46 6 84 41 52 74 3

2 …

…

…

…

…

…

…

Codebook

012

255254253

(20,45,…,76)

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AAD

Design HCT

101 102 102

100 102 110

102 111 113

1

1

1

1

'' ),(),(8

1),(

s t

jihtjsihjiAAD

875.38/)100102102102111102113102

110102102102102102101102(

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Hiding

127 12801111111 10000000

Host pixel h(i,j)

s(i,j)=00

HCT(i,j)=2

b(i,j)=127 mod 22=3

d(i,j)=0-3=-3

-22+1<=d(i,j)

<-(22-1)/2=-1.5

d’(i,j)=-3+22=1

h’(i,j)

127+1

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Index compression

129 128 130

134 128

10 01 11

00 I(x)

Encode: ‘0’+’01’RANG=4

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Index compression

2/)1()(

4/

DISP

DISP

THxIxI

codebookTH

134 128I(x-1) I(x)

Encode: ‘10’+’1’+’00110’

2/64134128

644/256

DISPTH

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Index compression

230 230 220

220 128I(x)

Encode: ‘11’+’10000000’

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Encrypt

Compressed index table is encrypted by DES cryptosystem suing the secret key sk

W, h, sno, Nc, k, rs, pk, RANG, and ThDIST are encrypted by DES cryptosystem also using the same secret key sk

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The secret extraction procedure

Extract w, h, sno, Nc, two random seeds key rs and pk, RANG, THDIFF and determine rmax.

Generate the VQ codebook with Nc codeword using H' with random seed rs.

Obtain a serial of random number by pk. To rebuild the original index table by RANG a

nd THDIFF.

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Experimental results

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Experimental results

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Experimental results

Comparative storage cost (unit: bits) of the proposed scheme (PS) and the proposed scheme without index compression (PS').

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Experimental results

Provide an average of 1.304dB image quality gain.

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Experimental results

Image qualities of the stego-images of the proposed scheme

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Experimental results

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Experimental results

Sno=1 Sno=2 Sno=3

GoldHill 54.222dB 51.264dB 47.788dB

Lena 53.923db 49.122dB 47.404dB

1024 codebook

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Conclusion

A novel image hiding scheme based on vector quantization is proposed.

The proposed scheme is secure.

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Comments

用 VQ將 secret images壓縮，所以 secret images取出後會失真。

將 index table再壓縮，隱藏數量變少。