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COLLUSION ATTACK RESISTANT WATERMARKING SCHEME FOR IMAGES USING DCT. Vikas Saxena , Prof. J. P. Gupta Jaypee Institute of Information Technology University, Noida, India Signal Processing and Communications Applications , 2007. SIU 2007. IEEE 15th Reporter : Chien-Ting Kuo. Outline.
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COLLUSION ATTACK RESISTANT WATERMARKING SCHEME FORIMAGES USING DCT Vikas Saxena , Prof. J. P. Gupta Jaypee Institute of Information Technology University, Noida, India Signal Processing and Communications Applications, 2007. SIU 2007. IEEE 15th Reporter : Chien-Ting Kuo
Outline • Introduction • Preliminaries • Proposed Scheme • Results • Conclusion
Introduction • This paper proposed a scheme by using classical middle frequency coefficients exchange scheme in conjunction with low frequency coefficient to make it collusion attack resistant. • Experimental results show the robustness of the proposed scheme against the JPEG compression and other common image manipulations.
Middle-band Coefficient Exchange Scheme Original image DCT DCT Block
Middle-band Coefficient Exchange Scheme DCT Block JPEG quantization table Encode 1 : DCT (4, 1) > DCT (2, 3); NO Exchange! Encode 0 : DCT(4, 1) <= DCT (2, 3); Exchange values -3 & 2
Proposed Scheme (encode 0) DCT Block JPEG quantization table DCT(0,1)>DCT(1,0)NO!! (5,2)<=(4,3) (5,1)<=(4,2) (6,3)<=(5,4) (3,2)<=(2,3)
Proposed Scheme (encode 1) DCT Block JPEG quantization table DCT(0,1)<= DCT (1,0)YES!! (5,2)>(4,3) (5,1)>(4,2) (6,3)>(5,4) (3,2)>(2,3)
Results PSNR of extracted watermark after JPEG compression
Results (JPEG compression at Q=20) Lena Baboon Pepper
Results (other common image manipulations) Extracted watermark from Lena’s image after Horizontal flipped, scaled, brightness/contrast adjusted and Noising (Left to Right, Top to bottom)
Conclusion • This paper presents a scheme for image watermarking by interchanging the middle-band coefficients in conjunction with low frequency coefficients of DCT domain. • Careful selection of pairs with randomness will make it more robust against the collusion attack.