WISP 2009, Budapest, Hungary

1

Increasing Watermarking Robustness using Turbo Codes

Corina Nafornita, Alexandru Isar, Maria Kovaci

Politehnica University of TimisoaraEmail: {corina.nafornita, alexandru.isar,

maria.kovaci@etc.upt.ro}

WISP 2009, Budapest, Hungary

2

Goal

Imperceptibility

Robustness

Capacity

Duo-binary turbo codes

Perceptual mask - DWT

Watermarking requirements

WISP 2009, Budapest, Hungary

3

Barni et al., 2001

Daubechies-6

Mask

Watermark

Original Marked

DWTIDWT

WISP 2009, Budapest, Hungary

4

Artifacts low resolution mask High resolution mask

Watermark easily erased All resolution levels

New approach: duo-binary turbo codes

Proposed solution

WISP 2009, Budapest, Hungary

5

New method

Bior2.2

New mask

Encoded Watermark

Original Marked

DWTIDWT

DBTC message

Select only higher coefficients!!!

WISP 2009, Budapest, Hungary

6

Mask estimation

Low resolution vs. High resolution (Barni et al.,2001) (Nafornita et al.,2006)

WISP 2009, Budapest, Hungary

7

Duo-Binary Turbo Code

8-state duo binary RSC encoder , rate 2/3. Encoder polynomials: 15 (feedback) and 13

(redundancy)

RSC r-ary

RSC r-ary

ilv

Input sequence

ru

1

1

c1

c2

u2

1

c =u0

11

S1

u1 u1

u2

S3S2

0

11 01

,d i j i j i j S

WISP 2009, Budapest, Hungary

8

Experiments

Lena•Test image Lena

•Message length: 768 bits

•Block size 7

•Threshold 10

•Watermark strength =9

•PSNR obtained 29.95 dB Watermarked Lena

WISP 2009, Budapest, Hungary

9

AWGN: σ=3.25…15

BER vs. BER vs. PSNR

WISP 2009, Budapest, Hungary

10

JPEG compression: Q=10…100

BER vs. quality factor

BER vs. PSNR

WISP 2009, Budapest, Hungary

11

Coded vs. Uncoded

Attack vs. BERBER

Uncoded DBTC

JPEG compression, Q=50, PSNR=32.94 dB

0.167132 0.001488

AWGN, =8, PSNR=29.29 dB

0.0885 3.25·10-4

WISP 2009, Budapest, Hungary

12

Conclusions

BER decreases in both cases when using turbo codes

Less severe attacks: perfect reconstruction, the attack modeled like an AWGN

channel with high SNR. Coding gain of DBTC higher than 2

dB