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A Hierarchical Digital Watermarking Method for Image Tamper Detection and Recovery

A Hierarchical Digital Watermarking Method for Image Tamper Detection and Recovery. Phen-Lan Lin, Chung-Kai Hsieh, and Po-Whei Huang Pattern Recognition Vol. 38, Issue 11, December 2005, pp. 2519-2529. Outline. Introduction The Proposed Method Watermark Embedding

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A Hierarchical Digital Watermarking Method for Image Tamper Detection and Recovery

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  1. A Hierarchical Digital Watermarking Method for Image Tamper Detection and Recovery Phen-Lan Lin, Chung-Kai Hsieh, and Po-Whei Huang Pattern Recognition Vol. 38, Issue 11, December 2005, pp. 2519-2529

  2. Outline • Introduction • The Proposed Method • Watermark Embedding • Hierarchical Tamper Detection • Tampered Image Recovery • Experimental Results • Conclusions • Comments

  3. Introduction • Watermarking Method for Image Tamper Detection and Recovery

  4. Block mapping sequence generation algorithm (4 ×4 pixels/block) • 1-1 mapping : X ' = [ f ( X ) = ( k × X ) mod N ] + 1, • X , X ' are the block number (∈ [0, N− 1 ]) • k is a secret key, (a prime and ∈ Z − {N 's factors }) • N is the total number of blocks in the image The original block The mapping of blocks X '=13×X mod 64 +1

  5. r Watermark Embedding (1/2) avg_As=(I1+I2+I3+I4)/4 avg_Bs=(I1+I2+I3+I4)/4 Block A avg_B=(I1+I2+…+I16)/16 Block B

  6. Watermark Embedding (2/2) Block A num: # of 1s in the 6 MSBs of avg_Bs avg_As=(69+78+35+46)/4=57=(00111001)2 r = 001110 Block B avg_Bs=(104+20+36+52)/4=53=(00110101)2 avg_B=(104+20+96+204+…+164)/16=97 v=0, p=1 104 104 Set 2LSBs to 0 22 22 39 39 55 54

  7. Hierarchical Tamper Detection (1/3) Level 1: for each sub-block B's of 2×2 pixels within block B' , verify v and p avg_B’s=(104+20+36+52)/4=53=00110101 avg_B’=(104+20+96+204+…+164)/16=97 v'=0, p'=1 ifv'is not equal to v OR if p'is not equal to p  This sub-Block is marked erroneous v=0, p=1 After Level 1 detection, each sub-block is marked valid of erroneous

  8. Hierarchical Tamper Detection (2/3) Level 2: For each block of size 4 × 4 pixels, mark this block erroneous if any of its sub-block is marked erroneous; otherwise, mark it valid. After Level 2 detection, each block is marked valid of erroneous Level 3: For each valid block of size 4×4 pixels, mark the block erroneous if there are five or more erroneous blocks in its 3×3 block-neighborhood, Most surrounding blocks of some valid block are erroneous, this block hardly remains valid.

  9. Hierarchical Tamper Detection (3/3) Level 4: only required for resisting against VQ attack, assume mapping sequence:B C valid Block C r = 001110(00) = 56 = avg_Cs avg_B’s=(68+76+32+44)/4=55 valid 57=00111001=00111000=56 avg_B’s avg_Cs Block B’

  10. Tampered Image Recovery Mapping sequence: A B valid Block B r = 001110(00) = 56 erroneous Tamped Block A Recovered Block A

  11. Experimental Results (1/7)

  12. Experimental Results (2/7)

  13. Experimental Results (3/7) • M1: Covering the whole image with leaf patterns, as depicted in Fig. 8(b). • M2: Covering the whole image with another image, as depicted in Fig. 8(c). • M3: Covering the whole image with fruit patterns, as depicted in Fig. 8(d). • M4: Spreading plenty of mist to the whole image, as depicted in Fig. 8(e).

  14. Experimental Results (4/7)

  15. Experimental Results (5/7)

  16. Experimental Results (6/7)

  17. Experimental Results (7/7)

  18. Conclusions • A hierarchical digital watermarking scheme for image tamper detection and restoration is proposed. • The proposed method uses parity check and intensity comparison with 3-Level detection for tamper detection. • The proposed method uses 2-LSBs of each pixel to restore the check bits and restore information.

  19. Comments • Level 4 detection resists against VQ attack (collage attack) • Something is wrong withLevel 4 detection • Reversible watermarking such as DE or histogram shifting is not suitable for tamper detection and recovery, this is because the bit-rate is low. • …

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