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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}. Robustness. Capacity. Imperceptibility. Goal. Duo-binary turbo codes.
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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
Robustness Capacity Imperceptibility Goal Duo-binary turbo codes Watermarking requirements Perceptual mask - DWT WISP 2009, Budapest, Hungary
Watermark IDWT DWT Marked Original Mask Barni et al., 2001 Daubechies-6 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
Encoded Watermark IDWT DWT Marked Original New mask New method DBTC message 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
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
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 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