# A copyright protection scheme

AI and Robotics

Nov 21, 2013 (4 years and 5 months ago)

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A copyright protection scheme
for digital images using visual
cryptography technique

Der
-
Chyuan Lou, Hao
-
Kuan Tso and Jiang
-
Lung Liu

The Computer Standards & Interfaces Volume: 29,
2006

Speaker
：黃資真

Outline

Introduction

Visual cryptography

Secret image generation

Watermark extraction

Conclusions

Introduction

Visual cryptography technique

Extract the feature from the protected image

Generate a secret image

Visual cryptography

Secret image generation (1/3)

I

A protected image

W’’

A watermark

K

A secret key

C

A codebook

L

Low sub
-
band

M

Middle sub
-
band

n

Normal
-
distribution random bit
-
sequence

f

Feature value

S

A secret image

Secret image generation (2/3)

Input

I, W, K, C

Output

S

Step 1

Step 2

Extract L and M.

Step 3

n = bit
-
sequence generated by K

'(,) (,) ( (,) (,))
L i j L i j n L i j M i j
   
Three
-
level

DWT

I

Secret image generation (3/3)

Step 4

Step 5

If f(i,j) = 1 and mod(i+j,4) = 0

If W(i,j) = 0

S(m,n) = [1 0]

Else

S(m,n) = [0 1]

End

End

Step 6

Register to CA for the secret image

1 (,)'(,)
(,)
0 (,)'(,)
if L i j L i j
f i j
if L i j L i j

Watermark extraction(1/4)

I’

A suspected image

S

Secret image

K

A secret key

C

Codebook

n

Normal
-
distribution random bit
-
sequence

W’’

A watermark

L’

Low sub
-
band

M’

Middle sub
-
band

f’

Extract the feature value

P

Public image

Watermark extraction(2/4)

Input

I’, S , K , C

Output

W’’

Step 1

Step 2

Extract L’ and M’

Step 3

n = generated by K

Three
-
level

DWT

I’

''(,)'(,) ('(,)'(,))
L i j L i j n L i j M i j
   
Watermark extraction(3/4)

Step 4

Step 5

If f ’(i,j) = 1 and
mod(i+j,4) = 0

P(m,n) = [1 0]

End

1 '(,)''(,)
'(,)
0 '(,)''(,)
if L i j L i j
f i j
if L i j L i j

Watermark extraction(4/4)

Step 6

Step 7

'
W S P
 
1
1
1 '(,) 1
''(,)
0 '(,) 1
m n
m n
m n
m n
if W m n
W i j
if W m n



Conclusions

A secret image is generated by utilizing the
codebook of visual cryptography.

The secret image is registered to CA for
further protection.

Watermark can be extracted by performing
the XOR operation between the secret image
and the public image.