1

Multiple layer data hiding scheme for medical images

Source: Computer Standards & InterfacesAuthors: Der-Chyuan Lou, Ming-Chiang Hu and Jiang-Lung LiuSpeaker: Chia-Chun Wu (吳佳駿 ) Date: 2008/11/14

2

Outline

Introduction Review of difference expansion

embedding The proposed method The experimental results Conclusions

3

Introduction Image Steganography

Cover image

Secret data: 0101…

Public channel(Ex: Internet)

Stego-image

SenderSender InterceptorInterceptor

ReceiverReceiver

Secret data: 0101…

Cover image

4

Review of difference expansion embedding (1/3) Tain’s reversible data embedding method (DE)

Pixel pair (x, y)

Pixel pair (206, 201)

m=203, d=5, b=1

Embedding:

' 2 , {0,1}d d b b

d'=(101b)2→(1011)2=11

' 1 '' , '

2 2

d dx m y m

x'=203+6=209, y'=203-5=198

New pixel pair (209,198)

2

x ym

d x y

5

Review of difference expansion embedding (2/3) Tain’s reversible data embedding method (DE)

Original pixel pair (206, 201)

m=203, d'=11

d'=11= (1011)2→b=1

x'=203+3=206, y'=203-2=201

New pixel pair (209,198)

d= (101)2=5

Pixel pair (206, 201)

m=203, d=5, b=1

d'=(101b)2→(1011)2=11

x'=203+6=209, y'=203-5=198

New pixel pair (209,198)

6

Review of difference expansion embedding (3/3) Overflow and underflow

• Overflow: (255, 254) → (256, 254)

• Underflow: (1, 0) →(1, -1) Solution:

' 2 (255 ), if 128 255

' 2 1, if 0 127

d m m

d m m

' 1 '' , '

2 2

d dx m y m

255

55

128 m=200

' 2 55 110d

127

10

0 m=10

' 2 10 1 21d

expandable

7

The proposed method (1/3)

Multiple-layer embedding concept

Cover image DE Stego-image

1. The visual quality of embedded image will be drastically degraded2. Cause the underflow or overflow problem3. Decrease the hiding capacity

Cover image Reduce DE Stego-image

8

The proposed method (2/3)

Pixel pair (206, 201)

m=203, h=5, b=1

New pixel pair (209,198)

h'=(101b)2→(1011)2=11

x'=203+6=209, y'=203-5=198

h'=5-21=3, b=1

h''=(11b)2→(111)2=7

x'=203+4=207, y'=203-3=200

New pixel pair (207,200)

Location map = 1

reduce

9

The proposed method (3/3)

x'=203+3=206, y'=203-2=201

New pixel pair (207, 200)

Location map = 1

Original pixel pair (206, 201)

m=203, h'=7

h'=7= (111)2→b=1

h'=3

h=3+21=5

10

The experimental results

11

Problem Double location map size

• 512×512 image• 131072 + 65536 = 196608 bits = 0.75 bpp

512×256

The first location map(1: expandable, 0: changeable)

(50% expandable, 50% changeable)

512×256×50%

The second location map

119628+113266-2*65536=101822 bits

12

Conclusions

The proposed method has remarkable improvement in the visual quality of the embedded image

The proposed method provide high-capacity