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

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

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

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

New method Bior2.2 DBTC Encoded Watermark Marked Original New mask message New mask Encoded Watermark Original Marked DWT IDWT Bior2.2 Select only higher coefficients!!! WISP 2009, Budapest, Hungary

Mask estimation Low resolution vs. High resolution (Barni et al.,2001) (Nafornita et al.,2006) WISP 2009, Budapest, Hungary

Duo-Binary Turbo Code 8-state duo binary RSC encoder , rate 2/3. RSC r-ary ilv Input sequence r u 1 c1 c2 u2 1 c =u0 S1 u1 S3 S2 8-state duo binary RSC encoder , rate 2/3. Encoder polynomials: 15 (feedback) and 13 (redundancy) WISP 2009, Budapest, Hungary

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

AWGN: σ=3.25…15 BER vs.  BER vs. PSNR WISP 2009, Budapest, Hungary

JPEG compression: Q=10…100 BER vs. quality factor BER vs. PSNR WISP 2009, Budapest, Hungary

Coded vs. Uncoded Attack vs. BER BER 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

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