1. Increasing Watermarking Robustness using Turbo Codes Corina Nafornita, Alexandru Isar, Maria Kovaci Politehnica University of Timisoara Email: {corina.nafornita, alexandru.isar, maria.kovaci@etc.upt.ro} WISP 2009, Budapest, Hungary

2. Robustness Capacity Imperceptibility Goal Duo-binary turbo codes Watermarking requirements Perceptual mask - DWT WISP 2009, Budapest, Hungary

3. Watermark IDWT DWT Marked Original Mask Barni et al., 2001 Daubechies-6 WISP 2009, Budapest, Hungary

4. Proposed solution • Artifacts  low resolution mask • High resolution mask • Watermark easily erased • All resolution levels • New approach: duo-binary turbo codes WISP 2009, Budapest, Hungary

5. Encoded Watermark IDWT DWT Marked Original New mask New method DBTC message Bior2.2 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. u2 u2 u1 u1 S3 S2 S1 0 1 1 1 0 1 1 1 c =u0 Input sequence r u RSC r-ary 1 c1 ilv RSC r-ary 1 c2 Duo-Binary Turbo Code • 8-state duo binary RSC encoder , rate 2/3. • Encoder polynomials: 15 (feedback) and 13 (redundancy) WISP 2009, Budapest, Hungary

8. Experiments • Test image Lena • Message length: 768 bits • Block size 7 • Threshold 10 • Watermark strength =9 • PSNR obtained 29.95 dB Lena 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 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 WISP 2009, Budapest, Hungary