Analysis and Design of Authentication Watermarking

1
Analysis and Design of Authentication Watermarking

• Jan. 22, 2004
• Chuhong Fei, Deepa Kundur, and Raymond Kwong

2
Content Authentication
Is the image credible?
Image
Channel
Sender (Alice)
Receiver (Bob)
legitimate distortions e.g. lossy compression
illegitimate distortions e.g. malicious tampering
by adversary (Oscar)
3
Semi-fragile Watermarking
Signature generation
Signature generation
011010
011010
Watermarkembedder
Watermark verification
Yes No
4
Requirements

• Robustness legitimate distortions
• Fragility illegitimate distortions
• Security malicious tampering
• Imperceptibility watermark embedding
• Complexity embedding, authenticating.

5
Previous Work

• SARI Lin Chang 2000
• Ad hoc design to lossy compression,
• Security concern Radhakrishnan Memon 2002
• Tuning a robust watermarking
• e.g. spread spectrum technique,
• Robustness is achieved, however, fragility is not
  well designed.

6
Admissible Set ?
illegitimate distortions
legitimate distortions
7
Watermark Layer Design
m
Distortion N
m
Watermarkembedder
Watermark verification
Yes No
Host image

• Objective
• Robustness legitimate distortions
• Fragility illegitimate distortions

8
Dirty Paper Code



admissible set
x
x
x
x



x
x
x
x



9
Random Legitimate Noise

• For instance, Gaussian Noise N(0,?2) is
• legitimate when ?2lt1,
• illegitimate otherwise.
• Idea find a deterministic set to distinguish two
  random sets
• Objective to minimize error probability.

10
Signature Layer Design

• Objective to enforce security

11
Previous Approach
Signature generation
Signature generation region
Watermark embedding region
12
New MSB Approach

• Originated from LSB embedding for fragile
  watermarking
• Walton 1995
• Wong 1998

Signature generation
MSB
LSB
13
key
Signature generation
Fundamental Voronoi region
For example Z/2Z
Coset leader
5.2 4 1 0.2
14
Security Analysis of MSB

• We show that the security of MSB is equivalent to
  that of the signature generation function,
• Message authentication code (MAC) is desired to
  generate signature.

15
An Example

• Uniformly distributed noise N is
• legitimate if ?lt1
• illegitimate if ?gt1.
• ? an n-D unit cube
• Nested lattice code Z/2Z
• MSB signature generation and LSB watermark
  embedding

16
Original and Watermarked Images
17
Legitimate and illegitimate Noises
18
Conclusion

• Admissible set ?
• Robustness
• Fragility
• MAC
• Security
• Lattice code
• Complexity and watermarking distortion